|
|
Free Programs for OS/390
The following programs are available for *free* download
from Dignus, LLC. These were last updated on Feb. 20th, 2001.
Each has been compiled with
Systems/C
- usually in a cross-platform environment.
Systems/C
has no runtime library requirements, there is nothing
more to download to run these programs.
They are made available free of charge, and unless
otherwise noted, are copyright Dignus, LLC.
Dignus provides NO WARRANTY, whatsoever, to these programs.
Use them at your own discretion.
We will update this page as more downloads become available.
Of course, nothing is totally free - while you're here, we hope
you'll take a moment and look at the information provided in
these web pages for
Systems/C.
- byacc - the Berkely YACC utility for parser generation.
- bwbasic - Bywater BASIC interpreter.
- dig - the DIG utility for querying DNS servers.
- flex - the Berkely Fast LEXical generator.
- grep - the standard GREP utility.
- indent - a program to "pretty print" C source.
- printps - a program to convert text to postscript.
- udsmtp - Batch SMTP client (send e-mail from jobs.) - UPDATED 2/18/2001
- what - the WHAT utility for object versions.
Note that the files are provided in TSO XMIT format. When downloading,
you should ensure that the file is copied in BINARY mode. Also, when
up-loading to your mainframe, you should ensure the up-loaded data set
is Fixed with an LRECL of 80, e.g. DCB=(RECFM=FB,LRECL=80,BLKSIZE=80*n).
A good way to ensure the data set is correct is to pre-allocate it.
Once the file has been properly transferred to your mainframe,
the TSO RECEIVE command is used to unload the data
set on OS/390. e.g.:
RECEIVE INDS(file-name)
Several people have had difficulting using their web browsers to
FTP the TSO transmit files. If so, you may want to directly use
your FTP program. All of the files listed here are available
via anonymous FTP at
dignus.com.
Simply ftp to dignus.com, and log in as the user anonymous.
Then change-directory to /pub/xmi where you will find
the various .XMI files. Be sure to download them in BINARY mode.
If you have any downloading problems, or questions feel free to
contact us.
For a small fee, we can place these .XMI files on an CD-ROM and
ship it to you.
printps
PRINTPS is a simple program which will accept text
and convert it to postscript. PRINTPS is Copyright 1991
by Gilles Vollant. The original sources were modified
to operate correctly on OS/390.
PRINTPS is provided in load-module format, as a TSO
transmit file. You should download the
PRINTPS.XMI
file and use the TSO RECEIVE command to receive it.
PRINTPS requires one argument - the name of the text
file to process. If a second argument is present,
it is the name of the output file, otherwise,
output is directed to the STDOUT DD.
File names follow the Systems/C C library conventions.
Please refer to the Systems/C documentation for
further information about Systems/C library file name
conventions.
For example, if the text to convert was available
in the TEXTIN DD name, the following would convert
that to postscript from TSO:
CALL my.load(PRINTPS) '//DDN:TEXTIN'
would convert TEXTIN to postscript, with the output
going to the STDOUT DD.
Similarly, the following JCL would convert a the file
MY.TEXT(FILE)
to postscript:
//CONV JOB
...
//PRINTPS EXEC PGM=PRINTPS,PARM='//DSN:MY.TEXT(FILE)'
//STEPLIB DD DSN=my.load,DISP=SHR
//STDOUT DD SYSOUT=*
//STDIN DD SYSOUT=*
//STDERR DD SYSOUT=*
Running PRINTPS with no arguments provides a short usage
note and the copyright notice.
The resulting file is a text file which represents a postscript
program. We have been successful printing several text files
this way.
indent
INDENT is a C "beautifier" program. Dignus, LLC has taken the
freely available BSD distribution and modified for running under OS/390.
Of course, this was compiled with
Systems/C.
You can download the
TSO transmit file for INDENT here.
This version is not the GNU version, and carries the following
copyright:
/*
* Copyright (c) 1985 Sun Microsystems, Inc.
* Copyright (c) 1980, 1993
* The Regents of the University of California. All rights reserved.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
The INDENT program has many options, which are described in this
manual page. (All file names should be specified in Systems/C format.)
INDENT(1) INDENT(1)
NAME
indent - indent and format C program source
SYNOPSIS
indent [input-file [output-file]] [-bad | -nbad] [-bap | -nbap]
[-bbb | -nbbb] [-bc | -nbc] [-bl] [-br] [-cn] [-cdn] [-cdb | -ncdb] [-ce
| -nce] [-cin] [-clin] [-dn] [-din] [-fc1 | -nfc1] [-in] [-ip | -nip]
[-ln] [-lcn] [-lp | -nlp] [-npro] [-pcs | -npcs] [-psl | -npsl] [-sc |
-nsc] [-sob | -nsob] [-st] [-troff] [-v | -nv]
DESCRIPTION
Indent is a C program formatter. It reformats the C program in the
input-file according to the switches. The switches which can be speci-
fied are described below. They may appear before or after the file
names.
NOTE: If you only specify an input-file, the formatting is directed
to STDOUT.
The options listed below control the formatting style imposed by indent.
-bad, -nbad If -bad is specified, a blank line is forced after every
block of declarations. Default: -nbad.
-bap, -nbap If -bap is specified, a blank line is forced after every
procedure body. Default: -nbap.
-bbb, -nbbb If -bbb is specified, a blank line is forced before every
block comment. Default: -nbbb.
-bc, -nbc If -bc is specified, then a newline is forced after each
comma in a declaration. -nbc turns off this option. De-
fault: -nbc.
-br, -bl Specifying -bl lines-up compound statements like this:
if (...)
{
code
}
Specifying -br (the default) makes them look like this:
if (...) {
code
}
-cn The column in which comments on code start. The default
is 33.
-cdn The column in which comments on declarations start. The
default is for these comments to start in the same column
as those on code.
-cdb, -ncdb Enables (disables) the placement of comment delimiters on
blank lines. With this option enabled, comments look
like this:
/*
* this is a comment
*/
Rather than like this:
/* this is a comment */
This only affects block comments, not comments to the
right of code. The default is -cdb.
-ce, -nce Enables (disables) forcing of `else's to cuddle up to the
immediately preceding `}'. The default is -ce.
-cin Sets the continuation indent to be n. Continuation lines
will be indented that far from the beginning of the first
line of the statement. Parenthesized expressions have
extra indentation added to indicate the nesting, unless
-lp is in effect. -ci defaults to the same value as -i.
-clin Causes case labels to be indented n tab stops to the
right of the containing switch statement. -cli0.5 causes
case labels to be indented half a tab stop. The default
is -cli0.
-dn Controls the placement of comments which are not to the
right of code. For example, -d1 means that such comments
are placed one indentation level to the left of code.
Specifying the default -d0 lines-up these comments with
the code. See the section on comment indentation below.
-din Specifies the indentation, in character positions, from a
declaration keyword to the following identifier. The de-
fault is -di16.
-dj, -ndj -dj left justifies declarations. -ndj indents declara-
tions the same as code. The default is -ndj.
-ei, -nei Enables (disables) special else-if processing. If it's
enabled, an if following an else will have the same in-
dentation as the preceding if statement. The default is
-ei.
-fc1, -nfc1 Enables (disables) the formatting of comments that start
in column 1. Often, comments whose leading `/' is in
column 1 have been carefully hand formatted by the pro-
grammer. In such cases, -nfc1 should be used. The de-
fault is -fc1.
-in The number of spaces for one indentation level. The de-
fault is 8.
-ip, -nip Enables (disables) the indentation of parameter declara-
tions from the left margin. The default is -ip.
-ln Maximum length of an output line. The default is 78.
-lp, -nlp Lines-up code surrounded by parenthesis in continuation
lines. If a line has a left paren which is not closed on
that line, then continuation lines will be lined up to
start at the character position just after the left
paren. For example, here is how a piece of continued
code looks with -nlp in effect:
p1 = first_procedure(second_procedure(p2, p3),
third_procedure(p4, p5));
With -lp in effect (the default) the code looks somewhat
clearer:
p1 = first_procedure(second_procedure(p2, p3),
third_procedure(p4, p5));
Inserting two more newlines we get:
p1 = first_procedure(second_procedure(p2,
p3),
third_procedure(p4,
p5));
-npro Causes the profile files, `./.indent.pro' and
`~/.indent.pro', to be ignored.
-pcs, -npcs If true (-pcs) all procedure calls will have a space in-
serted between the name and the `('. The default is
-npcs.
-psl, -npsl If true (-psl) the names of procedures being defined are
placed in column 1 - their types, if any, will be left on
the previous lines. The default is -psl.
-sc, -nsc Enables (disables) the placement of asterisks (`*'s) at
the left edge of all comments. The default is -sc.
-sob, -nsob If -sob is specified, indent will swallow optional blank
lines. You can use this to get rid of blank lines after
declarations. Default: -nsob.
-st Causes indent to take its input from stdin and put its
output to stdout.
-Ttypename Adds typename to the list of type keywords. Names accu-
mulate: -T can be specified more than once. You need to
specify all the typenames that appear in your program
that are defined by typedef - nothing will be harmed if
you miss a few, but the program won't be formatted as
nicely as it should. This sounds like a painful thing to
have to do, but it's really a symptom of a problem in C:
typedef causes a syntactic change in the language and in-
dent can't find all instances of typedef.
-troff Causes indent to format the program for processing by
troff(1). It will produce a fancy listing in much the
same spirit as vgrind(1). If the output file is not
specified, the default is standard output, rather than
formatting in place.
-v, -nv -v turns on `verbose' mode; -nv turns it off. When in
verbose mode, indent reports when it splits one line of
input into two or more lines of output, and gives some
size statistics at completion. The default is -nv.
You may set up your own `profile' of defaults to indent by creating a
file called //DDN:INDENTPR and including whatever switches you like.
If indent is run and a profile file exists, then it is read to set up the
program's defaults. Switches on the command line, though, always over-
ride profile switches. The switches should be separated by commas.
Comments
`Box' comments. Indent assumes that any comment with a dash or star imme-
diately after the start of comment (that is, `/*-' or `/**') is a comment
surrounded by a box of stars. Each line of such a comment is left un-
changed, except that its indentation may be adjusted to account for the
change in indentation of the first line of the comment.
Straight text. All other comments are treated as straight text. Indent
fits as many words (separated by blanks, tabs, or newlines) on a line as
possible. Blank lines break paragraphs.
Comment indentation
If a comment is on a line with code it is started in the `comment col-
umn', which is set by the -cn command line parameter. Otherwise, the
comment is started at n indentation levels less than where code is cur-
rently being placed, where n is specified by the -dn command line parame-
ter. If the code on a line extends past the comment column, the comment
starts further to the right, and the right margin may be automatically
extended in extreme cases.
Preprocessor lines
In general, indent leaves preprocessor lines alone. The only reformat-
ting that it will do is to straighten up trailing comments. It leaves
embedded comments alone. Conditional compilation (#ifdef...#endif) is
recognized and indent attempts to correctly compensate for the syntactic
peculiarities introduced.
C syntax
Indent understands a substantial amount about the syntax of C, but it has
a `forgiving' parser. It attempts to cope with the usual sorts of incom-
plete and misformed syntax. In particular, the use of macros like:
#define forever for(;;)
is handled properly.
FILES
//DDN:INDENTPR profile file
Here's some sample JCL for running INDENT. In this example,
the INDENTPR DD used to provide default arguments, the input
to format is the SOURCE DD, and the formatted output is
sent to the OUTPUT DD
//INDENT JOB
//STEP1 EXEC PGM=INDENT,PARM='//DDN:SOURCE,//DDN:OUTPUT'
//STEPLIB DD DSN=indent.load.module,DISP=SHR
//SYSPRINT DD SYSOUT=*
//SYSTERM DD SYSOUT=*
//STDOUT DD SYSOUT=*,LRECL=133,RECFM=FB
//STDERR DD SYSOUT=*,LRECL=133,RECFM=FB
//ASM DD SYSOUT=*,LRECL=133,RECFM=FB
//OUTPUT DD SYSOUT=*,LRECL=133,RECFM=FB
//STDIN DD *,LRECL=80
//INDENTPR DD *,LRECL=80
-bap -bad -bbb -nbc -br -cdb -ce -cli0.5 -di1 -nfc1 -i3 -nip -lp -ps1 -sc
//SOURCE DD *,LRECL=80
#pragma map(bar,"BAR")
bar(j)
int j;
{
printf("bar(%d)\n", j);
}
main()
{
int i;
double d;
long long l;
for(i=0;i<100;i++) {
bar(i+20);
}
i = 10;
d = 0.5;
}
//
grep
This is a version of the GREP (General Regular Expression Processor)
program, taken from http://www.snippets.org.
GREP will be familiar to UNIX and OE/MVS users, however, there
isn't a convenient version supplied for TSO or BATCH processing.
You can download the
TSO Transmit file for GREP here .
This version carries the following copyright notice:
/*
* The information in this document is subject to change
* without notice and should not be construed as a commitment
* by Digital Equipment Corporation or by DECUS.
*
* Neither Digital Equipment Corporation, DECUS, nor the authors
* assume any responsibility for the use or reliability of this
* document or the described software.
*
* Copyright (C) 1980, DECUS
*
* General permission to copy or modify, but not for profit, is
* hereby granted, provided that the above copyright notice is
* included and reference made to the fact that reproduction
* privileges were granted by DECUS.
*/
Running the GREP program with no arguments will provide usage
information, most of the basic GREP arguments are there.
Here is some example JCL which shows how GREP can be used
to locate specific lines in output.
//GREP JOB
//GREP1 EXEC PGM=GREP,PARM='-n,bar.*('
//STEPLIB DD DSN=grep.load.module,DISP=SHR
//SYSPRINT DD SYSOUT=*
//SYSTERM DD SYSOUT=*
//STDOUT DD SYSOUT=*,LRECL=133,RECFM=FB
//STDERR DD SYSOUT=*,LRECL=133,RECFM=FB
//STDIN DD *,LRECL=80
This line will not match
This line has bar( and will match
This line also has bar....( and will match
//
Or, you can call it from TSO. In this example,
we are examining the file MY.TEXT.FILE
for lines that contain the string "help".
CALL grep.load.module(GREP) 'help,//DSN:MY.TEXT.FILE' ASIS
Note that GREP expects the STDOUT and STDIN
DD's to be allocated.
what
WHAT shows versions of the object modules that were used to construct a program.Dignus, LLC has taken the freely available BSD distribution and modified for running under OS/390.
Of course, this was compiled with
Systems/C.
You can download the
TSO transmit file for WHAT here.
WHAT(1) General Commands Manual WHAT(1)
NAME
what - show what versions of object modules were used to construct a file
SYNOPSIS
what [-s] file ...
DESCRIPTION
The what utility searches each specified file for sequences of the form
``@(#)'' as inserted by the source code control system. It prints the
remainder of the string following this marker, up to a NUL character,
newline, double quote, ``>'' character, or backslash.
The following option is available:
-s Stop searching each file after the first match.
Exit status is 0 if any matches were found, otherwise 1.
BUGS
This is a rewrite of the SCCS command of the same name, and behavior may
not be identical.
SEE ALSO
ident(1), strings(1)
HISTORY
The what command appeared in 4.0BSD.
4th Berkeley Distribution June 6, 1993 1
Here's some sample JCL for running WHAT. In this example, the
program "PROG" in the load module MY.LOAD is examined.
//WHAT JOB
//STEP1 EXEC PGM=WHAT,PARM='//DSN:MY.LOAD(PROG)'
//STEPLIB DD DSN=what.load.module,DISP=SHR
//SYSPRINT DD SYSOUT=*
//SYSTERM DD SYSOUT=*
//STDOUT DD SYSOUT=*,LRECL=133,RECFM=FB
//STDERR DD SYSOUT=*,LRECL=133,RECFM=FB
//
You could also run WHAT from the TSO command line:
ALLOC DD(STDOUT) DD(*)
CALL what.load.module(WHAT) '//DSN:MY.LOAD(PROG)'
As shown above, WHAT expects at least the STDOUT DD to be defined.
udsmtp
Last Updated: 2/18/2001 - V1.5.2
UDSMTP is a Batch-SMTP (BSMTP) client which runs on OS/390. Using this
client, you can directly send e-mail from a job stream.
UDSMTP was written by Mike Porter of the University of Delaware
(mike@udel.edu). With Mike's assistance, Dignus, LLC has made the
modifications for it to be compiled with
Systems/C.
UDSMPT carries a GNU copyright as noted in the following README information
distributed with the sources:
UDSMTP 1.0.7
------------
UDSMTP - Simple SMTP Client.
Copyright (C) 1995, 1996 University of Delaware.
Portions Copyright by:
Copyright (C) 1987, 88, 89, 90, 91, 92, 93, 94
Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of
the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public
License along with this program in the file LICENSE; if not,
write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.
Contacts:
Primary author: Mike Porter mike@udel.edu
4 Brennen Ct.
Newark, DE 19713, USA
Copyright Holder: postmaster@udel.edu
Network and Systems Services
University of Delaware
192 S. Chapel St.
Newark, DE 19713
The sources for UDSMTP may be found at http://manatee.nss.udel.edu/
You can download the
TSO transmit file for UDSMTP here.
Running the UDSMTP program with the '--help' argument will provide a list
of options.
There is no manual page provided with UDSMTP, but running the program with
a '--help' argument produces output similar to the following:
Copyright (C) 1995-1999 University of Delaware
UDSMTP comes with ABSOLUTELY NO WARRANTY; for details
type `UDSMTP --license'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `UDSMTP --license' for details.
This program is a simple BSMTP handler. It makes one
connection and transfers all mail to the host using
the SMTP protocol.
The standard input consists of a file in BSMTP format.
The messages in the file are trasmitted using SMTP to
the --host with an smtp server on --port.
A resolver call is made for the name on --host; connection
attempts are made for each host listed as a MX for --host.
If no connect is made for any host, sleep for 5 minutes,
get new host MX list and try again. Never stops. If
--nomx is specified, then the MX record lookup is skipped.
An optional input file may be specified as the final parameter.
Here's some sample JCL for running UDSMTP. In this example,
the mail host (the value of the --host argument) is ponds.dignus.com,
our internal mail routing host here at Dignus, LLC. The message is
being sent from the user to the user
user@destination.com
//UDSMTP JOB
//STEP1 EXEC PGM=UDSMTP,PARM='--host,ponds.dignus.com'
//STEPLIB DD DSN=udsmtp.load.module,DISP=SHR
//SYSPRINT DD SYSOUT=*
//SYSTERM DD SYSOUT=*
//STDOUT DD SYSOUT=*,LRECL=133,RECFM=FB
//STDERR DD SYSOUT=*,LRECL=133,RECFM=FB
//STDIN DD *
HELO dignus.com
MAIL FROM:
RCPT TO:
DATA
To: user@destination.com
Test mail, sent from UDSMTP - the University of Delaware's
SMTP client. Of course, UDSMTP was compiled with Systems/C
and is using the Systems/C socket library.
This was sent from a job submitted on the mainframe.
.
QUIT
//
For more detailed information on UDSMTP, and other mainframe
related programs freely available from the University of Delaware
see http://manatee.nss.udel.edu/
or, contact Mike Porter.
dig
DIG provides information on the Domain Name System (DNS).
Dignus, LLC has taken the freely available BSD distribution and modified for running under OS/390.
Of course, this was compiled with
Systems/C.
The only difference between this DIG program and the one you may find on
a UNIX platform is the `ping' option. This version recognizes the option,
but doesn't execute the PING command.
You can download the
TSO transmit file for DIG here.
This is the manual page associated with DIG:
DIG(1) General Commands Manual DIG(1)
NAME
dig - send domain name query packets to name servers
SYNOPSIS
dig [@server] domain [] [] [+]
[-] [%comment]
DESCRIPTION
Dig (domain information groper) is a flexible command line tool which can
be used to gather information from the Domain Name System servers. Dig
has two modes: simple interactive mode for a single query, and batch mode
which executes a query for each in a list of several query lines. All
query options are accessible from the command line.
The usual simple use of dig will take the form:
dig @server domain query-type query-class
where:
server may be either a domain name or a dot-notation Internet ad-
dress. If this optional field is omitted, dig will attempt to
use the default name server for your machine.
Note: If a domain name is specified, this will be resolved
using the domain name system resolver (i.e., BIND). If your
system does not support DNS, you may have to specify a dot-
notation address. Alternatively, if there is a server at
your disposal somewhere, all that is required is that
/etc/resolv.conf be present and indicate where the default
name servers reside, so that server itself can be resolved.
See resolver(5) for information on /etc/resolv.conf. WARNING:
Changing /etc/resolv.conf will affect both the standard re-
solver library and (potentially) several programs which use
it. As an option, the user may set the environment variable
LOCALRES to name a file which is to be used instead of
/etc/resolv.conf standard resolver (LOCALRESis specific to
the dig resolver and is not referenced by the). If the
LOCALRES variable is not set or the specified file is not
readable, then /etc/resolv.conf will be used.
domain is the domain name for which you are requesting information.
See the -x option (documented in the OTHER OPTIONS subsection
of this section) for convenient way to specify inverse ad-
dress query.
query-type is the type of information (DNS query type) that you are re-
questing. If omitted, the default is ``a'' (T_A = address).
The following types are recognized:
a T_A network address
any T_ANY all/any information about specified domain
mx T_MX mail exchanger for the domain
ns T_NS name servers
soa T_SOA zone of authority record
hinfo T_HINFO host information
axfr T_AXFR zone transfer (must ask an authoritative
server)
txt T_TXT arbitrary number of strings
(See RFC 1035 for the complete list.)
query-class
is the network class requested in the query. If omitted, the
default is ``in'' (C_IN = Internet). The following classes
are recognized:
in C_IN Internet class domain
any C_ANY all/any class information
(See RFC 1035 for the complete list.)
Note: ``Any'' can be used to specify a class and/or a type of
query. Dig will parse the first occurrence of ``any'' to
mean query-type = T_ANY. To specify query-class = C_ANY, you
must either specify ``any'' twice, or set query-class using
the -c option (see below).
OTHER OPTIONS
%ignored-comment
``%'' is used to included an argument that is simply not
parsed. This may be useful if running dig in batch mode.
Instead of resolving every @server-domain-name in a list of
queries, you can avoid the overhead of doing so, and still
have the domain name on the command line as a reference. Ex-
ample:
dig @128.9.0.32 %venera.isi.edu mx isi.edu
-
``-'' is used to specify an option which affects the opera-
tion of dig. The following options are currently available
(although not guaranteed to be useful):
-x dot-notation-address
Convenient form to specify inverse address map-
ping. Instead of ``dig 32.0.9.128.in-
addr.arpa'', one can simply ``dig -x
128.9.0.32''.
-f file File for dig batch mode. The file contains a list
of query specifications ( dig command lines)
which are to be executed successively. Lines be-
ginning with `;', `#', or `\n' are ignored. Oth-
er options may still appear on command line, and
will be in effect for each batch query.
-T time Time in seconds between start of successive
queries when running in batch mode. Can be used
to keep two or more batch dig commands running
roughly in sync. Default is zero.
-p port Port number. Query a name server listening to a
non-standard port number. Default is 53.
-P[ping-string]
After query returns, execute a ping(8) command
for response time comparison. This rather unele-
gantly makes a call to the shell. The last three
lines of statistics is printed for the command:
ping -s -server_name -56 -3
If the optional ``ping_string'' is present, it
replaces ``ping -s'' in the shell command.
-t query-type
Specify type of query. May specify either an in-
teger value to be included in the type field or
use the abbreviated mnemonic as discussed above
(i.e., mx = T_MX).
-c query-class
Specify class of query. May specify either an in-
teger value to be included in the class field or
use the abbreviated mnemonic as discussed above
(i.e., in = C_IN).
-envsav This flag specifies that the dig environment (de-
faults, print options, etc.), after all of the
arguments are parsed, should be saved to a file
to become the default environment. This is use-
ful if you do not like the standard set of de-
faults and do not desire to include a large num-
ber of options each time dig is used. The envi-
ronment consists of resolver state variable
flags, timeout, and retries as well as the flags
detailing dig output (see below). If the shell
environment variable LOCALDEF is set to the name
of a file, this is where the default dig environ-
ment is saved. If not, the file ``DiG.env'' is
created in the current working directory.
Note: LOCALDEF is specific to the dig resolver,
and will not affect operation of the standard re-
solver library.
Each time dig is executed, it looks for
``./DiG.env'' or the file specified by the shell
environment variable LOCALDEF. If such file ex-
ists and is readable, then the environment is re-
stored from this file before any arguments are
parsed.
-envset This flag only affects batch query runs. When
``-envset'' is specified on a line in a dig batch
file, the dig environment after the arguments are
parsed becomes the default environment for the
duration of the batch file, or until the next
line which specifies ``-envset''.
-[no] stick
This flag only affects batch query runs. It
specifies that the dig environment (as read ini-
tially or set by ``-envset'' switch) is to be re-
stored before each query (line) in a dig batch
file. The default ``-nostick'' means that the
dig environment does not stick, hence options
specified on a single line in a dig batch file
will remain in effect for subsequent lines (i.e.
they are not restored to the ``sticky'' default).
+
``+'' is used to specify an option to be changed in the query
packet or to change dig output specifics. Many of these are
the same parameters accepted by nslookup(8). If an option
requires a parameter, the form is as follows:
+ keyword [=value]
Most keywords can be abbreviated. Parsing of the ``+'' op-
tions is very simplistic -- a value must not be separated
from its keyword by white space. The following keywords are
currently available:
Keyword Abbrev. Meaning [default]
[no] debug (deb) turn on/off debugging mode [deb]
[no] d2 turn on/off extra debugging mode
[nod2]
[no] recurse (rec) use/don't use recursive lookup [rec]
retry=# (ret) set number of retries to # [4]
time=# (ti) set timeout length to # seconds [4]
[no] ko keep open option (implies vc) [noko]
[no] vc use/don't use virtual circuit [novc]
[no] defname (def) use/don't use default domain name
[def]
[no] search (sea) use/don't use domain search list
[sea]
domain=NAME (do) set default domain name to NAME
[no] ignore (i) ignore/don't ignore trunc. errors
[noi]
[no] primary (pr) use/don't use primary server [nopr]
[no] aaonly (aa) authoritative query only flag [noaa]
[no] cmd echo parsed arguments [cmd]
[no] stats (st) print query statistics [st]
[no] Header (H) print basic header [H]
[no] header (he) print header flags [he]
[no] ttlid (tt) print TTLs [tt]
[no] cl print class info [nocl]
[no] qr print outgoing query [noqr]
[no] reply (rep) print reply [rep]
[no] ques (qu) print question section [qu]
[no] answer (an) print answer section [an]
[no] author (au) print authoritative section [au]
[no] addit (ad) print additional section [ad]
pfdef set to default print flags
pfmin set to minimal default print flags
pfset=# set print flags to # (# can be
hex/octal/decimal)
pfand=# bitwise and print flags with #
pfor=# bitwise or print flags with #
The retry and time options affect the retransmission strategy
used by the resolver library when sending datagram queries.
The algorithm is as follows:
for i = 0 to retry - 1
for j = 1 to num_servers
send_query
wait((time * (2**i)) / num_servers)
end
end
(Note: dig always uses a value of 1 for ``num_servers''.)
DETAILS
Dig once required a slightly modified version of the BIND resolver(3) li-
brary. As of BIND 4.9, BIND's resolver has been augmented to work prop-
erly with dig. Essentially, dig is a straight-forward (albeit not pretty)
effort of parsing arguments and setting appropriate parameters. Dig uses
resolver(3) routines res_init(), res_mkquery(), res_send() as well as ac-
cessing the _res structure.
ENVIRONMENT
LOCALRES file to use in place of Pa /etc/resolv.conf
LOCALDEF default environment file
See also the explanation of the -envsav, -envset, and -[no] stick op-
tions, above.
FILES
/etc/resolv.conf
initial domain name and name server addresses
./DiG.env default save file for default options
SEE ALSO
named(8), resolver(3), resolver(5), nslookup(8).
STANDARDS
RFC 1035.
AUTHOR
Steve Hotz hotz@isi.edu
ACKNOWLEDGMENTS
Dig uses functions from nslookup(8) authored by Andrew Cherenson.
BUGS
Dig has a serious case of "creeping featurism" -- the result of consider-
ing several potential uses during it's development. It would probably
benefit from a rigorous diet. Similarly, the print flags and granularity
of the items they specify make evident their rather ad hoc genesis.
Dig does not consistently exit nicely (with appropriate status) when a
problem occurs somewhere in the resolver (NOTE:most of the common exit
cases are handled). This is particularly annoying when running in batch
mode. If it exits abnormally (and is not caught), the entire batch
aborts; when such an event is trapped, dig simply continues with the next
query.
4th Berkeley Distribution August 30, 1990 5
Here's some sample JCL for running DIG. In this example, DIG
looks up information from the Domain Name System about the "dignus.com"
domain.
//DIG JOB
//STEP1 EXEC PGM=DIG,PARM='dignus.com'
//STEPLIB DD DSN=dig.load.module,DISP=SHR
//SYSPRINT DD SYSOUT=*
//SYSTERM DD SYSOUT=*
//STDOUT DD SYSOUT=*,LRECL=133,RECFM=FB
//STDERR DD SYSOUT=*,LRECL=133,RECFM=FB
//
You could also run DIG from the TSO command line:
ALLOC DD(STDOUT) DD(*)
CALL dig.load.module(DIG) '-x,dignus.com' asis
This example looks up the inverse address mapping.
Note that arguments are seperated by commas, as that is
how the Systems/C library processes the OS/390 argument string.
Also DIG expects at least the STDOUT DD to be defined.
bwbasic
BWBASIC is a BASIC language interpreted written by Ted A. Campbell.
It is available under the GNU public license. If you'd like a copy of the
sources, please send a note to Dignus, LLC.
Of course, this was compiled with
Systems/C.
You can download the
TSO transmit file for BWBASIC here.
The documentation describes the language BWBASIC accepts. To execute BWBASIC, you should
appropriately define your STDIN, STDOUT and STDERROR DD statements and
CALL bwbasic, as in:
ALLOC DD(STDIN) DA(*)
ALLOC DD(STDOUT) DA(*)
ALLOC DD(STDERR) DA(*)
CALL bwbasic.load(BWBASIC)
Or, alternatively - it can be run batch with JCL similar to the following.
This example will input a file that implements Pascal's triangle, and
run the program:
//TOSIVP JOB
//STEP1 EXEC PGM=BWBASIC,
// PARM=''
//STDOUT DD SYSOUT=*
//STDERR DD SYSOUT=*,LRECL=133,BLKSIZE=1330,RECFM=FB
//STDIN DD *,LRECL=80
load "//ddn:PASCALTR"
run
//PASCALTR DD *,LRECL=80
100 dim pascal(14,14)
110 pascal(1,1) = 1
120 for i = 2 to 14
130 pascal(i,1) = 1
140 for j = 2 to i
150 pascal(i,j) = pascal(i-1,j)+pascal(i-1,j-1)
160 next j
170 next i
180 for i = 1 to 14
190 print i-1; ": ";
200 for j = 1 to i
210 print pascal(i,j);
220 next j
230 print
240 next i
250 end
//
byacc
BYACC is the Berkely YACC (Yet Another Compiler Compiler) program
that constructs LALR(1) parsers.
Dignus, LLC has taken the freely available BSD distribution and modified it
for running under OS/390.
Of course, this was compiled with
Systems/C
and linked with the
Systems/C
library.
To learn more about Berkely YACC - we suggest the text lex and yacc
by Tony Mason and Doug Brown, from O'Reilly & Associates, Inc.
Berkely Yacc carries the following copyright notice:
Copyright (c) 1989 The Regents of the University of California.
All rights reserved.
This code is derived from software contributed to Berkeley by
Robert Paul Corbett.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. All advertising materials mentioning features or use of this software
must display the following acknowledgement:
This product includes software developed by the University of
California, Berkeley and its contributors.
4. Neither the name of the University nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
You can download the
TSO transmit file for BYACC here.
YACC(1) YACC(1)
NAME
yacc - an LALR(1) parser generator
SYNOPSIS
yacc [-dlrtv] [-b file_prefix] [-o output_filename] [-p symbol_prefix]
filename
DESCRIPTION
Yacc reads the grammar specification in the file filename and generates
an LR(1) parser for it. The parsers consist of a set of LALR(1) parsing
tables and a driver routine written in the C programming language. Yacc
normally writes the parse tables and the driver routine to the file
//DDN:ytabc.
The following options are available:
-b file_prefix
Change the prefix prepended to the output file names to the
string denoted by file_prefix. The default prefix is the charac-
ter y.
-d Cause the header file //DDN:ytabh to be written.
-l If the -l option is not specified, yacc will insert #line direc-
tives in the generated code. The #line directives let the C com-
piler relate errors in the generated code to the user's original
code. If the -l option is specified, yacc will not insert the
#line directives. Any #line directives specified by the user
will be retained.
-o output_filename
Cause yacc to write the generated code to output_filename instead
of the default file, //DDN:ytabc.
-p symbol_prefix
Change the prefix prepended to yacc-generated symbols to the
string denoted by symbol_prefix. The default prefix is the string
yy.
-r Cause yacc to produce separate files for code and tables. The
code file is named //DDN:ycodec, and the tables file is named
//DDN:ytabc.
-t Change the preprocessor directives generated by yacc so that de-
bugging statements will be incorporated in the compiled code.
-v Cause a human-readable description of the generated parser to be
written to the file //DDN:yout.
If the environment variable TMPDIR is set, the string denoted by TMPDIR
will be used as the name of the directory where the temporary files are
created.
FILES
//DDN:ycodec
//DDN:ytabc
//DDN:ytabh
//DDN:yout
//DDN:action
//DDN:text
//DDN:union
DIAGNOSTICS
If there are rules that are never reduced, the number of such rules is
reported on standard error. If there are any LALR(1) conflicts, the num-
ber of conflicts is reported on standard error.
BSD May 24, 1993 2
Here's some sample JCL for running BYACC. In this example, the
YACC description /DDN:YACCIN is read producing //DDN:YTABC (the C source
to compile) and //DDN:YTABH (the header that defines token values),
and //DDN:YOUT - which is the "human readable" description of
the generated parser.
Also notice the temporary files needed by BYACC, //DDN:ACTION, //DDN:TEXT
and //DDN:UNION. Without proper allocations of these, BYACC will not
operate. The LRECL on these files should be large enough to accomodate
the widest line in the yacc description input.
//BYACC JOB
//STEP1 EXEC PGM=BYACC,PARM='-v,-d,//DDN:YACCIN'
//STEPLIB DD DSN=byacc.module.load,DISP=SHR
//SYSUDUMP DD SYSOUT=*
//SYSPRINT DD SYSOUT=*
//SYSTERM DD SYSOUT=*
//STDOUT DD SYSOUT=*,LRECL=133,RECFM=FB
//STDERR DD SYSOUT=*,LRECL=133,RECFM=FB
//SOURCE DD SYSOUT=*,LRECL=133,RECFM=FB
//ACTION DD DSN=&&ACTION,UNIT=VIO,DISP=(NEW,PASS),
// SPACE=(32000,(30,30)),
// DCB=(RECFM=FB,LRECL=80,BLKSIZE=3200)
//TEXT DD DSN=&&TEXT,UNIT=VIO,DISP=(NEW,PASS),
// SPACE=(32000,(30,30)),
// DCB=(RECFM=FB,LRECL=80,BLKSIZE=3200)
//UNION DD DSN=&&UNION,UNIT=VIO,DISP=(NEW,PASS),
// SPACE=(32000,(30,30)),
// DCB=(RECFM=FB,LRECL=80,BLKSIZE=3200)
//YTABC DD SYSOUT=*,LRECL=133,RECFM=FB
//YTABH DD SYSOUT=*,LRECL=133,RECFM=FB
//YOUT DD SYSOUT=*,LRECL=133,RECFM=FB
//YACCIN DD *,LRECL=80
... yacc description file ...
//
flex
FLEX is the Berkely Fast LEXical analyzer generator, compatible with AT&T lex.
Dignus, LLC has taken the freely available BSD distribution and modified it
for running under OS/390.
Of course, this was compiled with
Systems/C
and linked with the
Systems/C
library.
To learn more about Berkely YACC - we suggest the text lex and yacc
by Tony Mason and Doug Brown, from O'Reilly & Associates, Inc.
FLEX carries the following copyright requirements
"This product includes software developed by the
University of California, Berkeley and its contributors"
You can download the
TSO transmit file for FLEX here.
The "manual page" for FLEX follows:
FLEX(1) FLEX(1)
NAME
flex - fast lexical analyzer generator
SYNOPSIS
flex [-bcdfhilnpstvwBFILTV78+? -C[aefFmr] -ooutput -Ppre-
fix -Sskeleton] [--help --version] [filename ...]
OVERVIEW
This manual describes flex, a tool for generating programs
that perform pattern-matching on text. The manual
includes both tutorial and reference sections:
Description
a brief overview of the tool
Some Simple Examples
Format Of The Input File
Patterns
the extended regular expressions used by flex
How The Input Is Matched
the rules for determining what has been matched
Actions
how to specify what to do when a pattern is matched
The Generated Scanner
details regarding the scanner that flex produces;
how to control the input source
Start Conditions
introducing context into your scanners, and
managing "mini-scanners"
Multiple Input Buffers
how to manipulate multiple input sources; how to
scan from strings instead of files
End-of-file Rules
special rules for matching the end of the input
Miscellaneous Macros
a summary of macros available to the actions
Values Available To The User
a summary of values available to the actions
Interfacing With Yacc
connecting flex scanners together with yacc parsers
Options
flex command-line options, and the "%option"
Version 2.5 April 1995 1
FLEX(1) FLEX(1)
directive
Performance Considerations
how to make your scanner go as fast as possible
Generating C++ Scanners
the (experimental) facility for generating C++
scanner classes
Incompatibilities With Lex And POSIX
how flex differs from AT&T lex and the POSIX lex
standard
Diagnostics
those error messages produced by flex (or scanners
it generates) whose meanings might not be apparent
Files
files used by flex
Deficiencies / Bugs
known problems with flex
See Also
other documentation, related tools
Author
includes contact information
DESCRIPTION
flex is a tool for generating scanners: programs which
recognized lexical patterns in text. flex reads the given
input files, or its standard input if no file names are
given, for a description of a scanner to generate. The
description is in the form of pairs of regular expressions
and C code, called rules. flex generates as output a C
source file, //ddn:lexyyc, which defines a routine yylex().
This file is compiled and linked with the -lfl library to
produce an executable. When the executable is run, it
analyzes its input for occurrences of the regular expres-
sions. Whenever it finds one, it executes the correspond-
ing C code.
SOME SIMPLE EXAMPLES
First some simple examples to get the flavor of how one
uses flex. The following flex input specifies a scanner
which whenever it encounters the string "username" will
replace it with the user's login name:
%%
username printf( "%s", getlogin() );
By default, any text not matched by a flex scanner is
Version 2.5 April 1995 2
FLEX(1) FLEX(1)
copied to the output, so the net effect of this scanner is
to copy its input file to its output with each occurrence
of "username" expanded. In this input, there is just one
rule. "username" is the pattern and the "printf" is the
action. The "%%" marks the beginning of the rules.
Here's another simple example:
int num_lines = 0, num_chars = 0;
%%
\n ++num_lines; ++num_chars;
. ++num_chars;
%%
main()
{
yylex();
printf( "# of lines = %d, # of chars = %d\n",
num_lines, num_chars );
}
This scanner counts the number of characters and the num-
ber of lines in its input (it produces no output other
than the final report on the counts). The first line
declares two globals, "num_lines" and "num_chars", which
are accessible both inside yylex() and in the main() rou-
tine declared after the second "%%". There are two rules,
one which matches a newline ("\n") and increments both the
line count and the character count, and one which matches
any character other than a newline (indicated by the "."
regular expression).
A somewhat more complicated example:
/* scanner for a toy Pascal-like language */
%{
/* need this for the call to atof() below */
#include
%}
DIGIT [0-9]
ID [a-z][a-z0-9]*
%%
{DIGIT}+ {
printf( "An integer: %s (%d)\n", yytext,
atoi( yytext ) );
}
{DIGIT}+"."{DIGIT}* {
printf( "A float: %s (%g)\n", yytext,
Version 2.5 April 1995 3
FLEX(1) FLEX(1)
atof( yytext ) );
}
if|then|begin|end|procedure|function {
printf( "A keyword: %s\n", yytext );
}
{ID} printf( "An identifier: %s\n", yytext );
"+"|"-"|"*"|"/" printf( "An operator: %s\n", yytext );
"{"[^}\n]*"}" /* eat up one-line comments */
[ \t\n]+ /* eat up whitespace */
. printf( "Unrecognized character: %s\n", yytext );
%%
main( argc, argv )
int argc;
char **argv;
{
++argv, --argc; /* skip over program name */
if ( argc > 0 )
yyin = fopen( argv[0], "r" );
else
yyin = stdin;
yylex();
}
This is the beginnings of a simple scanner for a language
like Pascal. It identifies different types of tokens and
reports on what it has seen.
The details of this example will be explained in the fol-
lowing sections.
FORMAT OF THE INPUT FILE
The flex input file consists of three sections, separated
by a line with just %% in it:
definitions
%%
rules
%%
user code
The definitions section contains declarations of simple
name definitions to simplify the scanner specification,
and declarations of start conditions, which are explained
in a later section.
Version 2.5 April 1995 4
FLEX(1) FLEX(1)
Name definitions have the form:
name definition
The "name" is a word beginning with a letter or an under-
score ('_') followed by zero or more letters, digits, '_',
or '-' (dash). The definition is taken to begin at the
first non-white-space character following the name and
continuing to the end of the line. The definition can
subsequently be referred to using "{name}", which will
expand to "(definition)". For example,
DIGIT [0-9]
ID [a-z][a-z0-9]*
defines "DIGIT" to be a regular expression which matches a
single digit, and "ID" to be a regular expression which
matches a letter followed by zero-or-more letters-or-dig-
its. A subsequent reference to
{DIGIT}+"."{DIGIT}*
is identical to
([0-9])+"."([0-9])*
and matches one-or-more digits followed by a '.' followed
by zero-or-more digits.
The rules section of the flex input contains a series of
rules of the form:
pattern action
where the pattern must be unindented and the action must
begin on the same line.
See below for a further description of patterns and
actions.
Finally, the user code section is simply copied to
//ddn:lexyyc verbatim. It is used for companion routines
which call or are called by the scanner. The presence of
this section is optional; if it is missing, the second %%
in the input file may be skipped, too.
In the definitions and rules sections, any indented text
or text enclosed in %{ and %} is copied verbatim to the
output (with the %{}'s removed). The %{}'s must appear
unindented on lines by themselves.
In the rules section, any indented or %{} text appearing
before the first rule may be used to declare variables
which are local to the scanning routine and (after the
Version 2.5 April 1995 5
FLEX(1) FLEX(1)
declarations) code which is to be executed whenever the
scanning routine is entered. Other indented or %{} text
in the rule section is still copied to the output, but its
meaning is not well-defined and it may well cause compile-
time errors (this feature is present for POSIX compliance;
see below for other such features).
In the definitions section (but not in the rules section),
an unindented comment (i.e., a line beginning with "/*")
is also copied verbatim to the output up to the next "*/".
PATTERNS
The patterns in the input are written using an extended
set of regular expressions. These are:
x match the character 'x'
. any character (byte) except newline
[xyz] a "character class"; in this case, the pattern
matches either an 'x', a 'y', or a 'z'
[abj-oZ] a "character class" with a range in it; matches
an 'a', a 'b', any letter from 'j' through 'o',
or a 'Z'
[^A-Z] a "negated character class", i.e., any character
but those in the class. In this case, any
character EXCEPT an uppercase letter.
[^A-Z\n] any character EXCEPT an uppercase letter or
a newline
r* zero or more r's, where r is any regular expression
r+ one or more r's
r? zero or one r's (that is, "an optional r")
r{2,5} anywhere from two to five r's
r{2,} two or more r's
r{4} exactly 4 r's
{name} the expansion of the "name" definition
(see above)
"[xyz]\"foo"
the literal string: [xyz]"foo
\X if X is an 'a', 'b', 'f', 'n', 'r', 't', or 'v',
then the ANSI-C interpretation of \x.
Otherwise, a literal 'X' (used to escape
operators such as '*')
\0 a NUL character (ASCII code 0)
\123 the character with octal value 123
\x2a the character with hexadecimal value 2a
(r) match an r; parentheses are used to override
precedence (see below)
rs the regular expression r followed by the
regular expression s; called "concatenation"
r|s either an r or an s
Version 2.5 April 1995 6
FLEX(1) FLEX(1)
r/s an r but only if it is followed by an s. The
text matched by s is included when determining
whether this rule is the "longest match",
but is then returned to the input before
the action is executed. So the action only
sees the text matched by r. This type
of pattern is called trailing context".
(There are some combinations of r/s that flex
cannot match correctly; see notes in the
Deficiencies / Bugs section below regarding
"dangerous trailing context".)
^r an r, but only at the beginning of a line (i.e.,
which just starting to scan, or right after a
newline has been scanned).
r$ an r, but only at the end of a line (i.e., just
before a newline). Equivalent to "r/\n".
Note that flex's notion of "newline" is exactly
whatever the C compiler used to compile flex
interprets '\n' as; in particular, on some DOS
systems you must either filter out \r's in the
input yourself, or explicitly use r/\r\n for "r$".
<s>r an r, but only in start condition s (see
below for discussion of start conditions)
<s1,s2,s3>r
same, but in any of start conditions s1,
s2, or s3
<*>r an r in any start condition, even an exclusive one.
<<EOF>> an end-of-file
<s1,s2><<EOF>>
an end-of-file when in start condition s1 or s2
Note that inside of a character class, all regular expres-
sion operators lose their special meaning except escape
('\') and the character class operators, '-', ']', and, at
the beginning of the class, '^'.
The regular expressions listed above are grouped according
to precedence, from highest precedence at the top to low-
est at the bottom. Those grouped together have equal
precedence. For example,
foo|bar*
is the same as
(foo)|(ba(r*))
since the '*' operator has higher precedence than concate-
nation, and concatenation higher than alternation ('|').
Version 2.5 April 1995 7
FLEX(1) FLEX(1)
This pattern therefore matches either the string "foo" or
the string "ba" followed by zero-or-more r's. To match
"foo" or zero-or-more "bar"'s, use:
foo|(bar)*
and to match zero-or-more "foo"'s-or-"bar"'s:
(foo|bar)*
In addition to characters and ranges of characters, char-
acter classes can also contain character class expres-
sions. These are expressions enclosed inside [: and :]
delimiters (which themselves must appear between the '['
and ']' of the character class; other elements may occur
inside the character class, too). The valid expressions
are:
[:alnum:] [:alpha:] [:blank:]
[:cntrl:] [:digit:] [:graph:]
[:lower:] [:print:] [:punct:]
[:space:] [:upper:] [:xdigit:]
These expressions all designate a set of characters equiv-
alent to the corresponding standard C isXXX function. For
example, [:alnum:] designates those characters for which
isalnum() returns true - i.e., any alphabetic or numeric.
Some systems don't provide isblank(), so flex defines
[:blank:] as a blank or a tab.
For example, the following character classes are all
equivalent:
[[:alnum:]]
[[:alpha:][:digit:]
[[:alpha:]0-9]
[a-zA-Z0-9]
If your scanner is case-insensitive (the -i flag), then
[:upper:] and [:lower:] are equivalent to [:alpha:].
Some notes on patterns:
- A negated character class such as the example "[^A-
Z]" above will match a newline unless "\n" (or an
equivalent escape sequence) is one of the charac-
ters explicitly present in the negated character
class (e.g., "[^A-Z\n]"). This is unlike how many
other regular expression tools treat negated char-
acter classes, but unfortunately the inconsistency
is historically entrenched. Matching newlines
means that a pattern like [^"]* can match the
entire input unless there's another quote in the
Version 2.5 April 1995 8
FLEX(1) FLEX(1)
input.
- A rule can have at most one instance of trailing
context (the '/' operator or the '$' operator).
The start condition, '^', and "<<EOF>>" patterns
can only occur at the beginning of a pattern, and,
as well as with '/' and '$', cannot be grouped
inside parentheses. A '^' which does not occur at
the beginning of a rule or a '$' which does not
occur at the end of a rule loses its special prop-
erties and is treated as a normal character.
The following are illegal:
foo/bar$
<sc1>foo<sc2>bar
Note that the first of these, can be written
"foo/bar\n".
The following will result in '$' or '^' being
treated as a normal character:
foo|(bar$)
foo|^bar
If what's wanted is a "foo" or a bar-followed-by-a-
newline, the following could be used (the special
'|' action is explained below):
foo |
bar$ /* action goes here */
A similar trick will work for matching a foo or a
bar-at-the-beginning-of-a-line.
HOW THE INPUT IS MATCHED
When the generated scanner is run, it analyzes its input
looking for strings which match any of its patterns. If
it finds more than one match, it takes the one matching
the most text (for trailing context rules, this includes
the length of the trailing part, even though it will then
be returned to the input). If it finds two or more
matches of the same length, the rule listed first in the
flex input file is chosen.
Once the match is determined, the text corresponding to
the match (called the token) is made available in the
global character pointer yytext, and its length in the
global integer yyleng. The action corresponding to the
matched pattern is then executed (a more detailed descrip-
tion of actions follows), and then the remaining input is
scanned for another match.
Version 2.5 April 1995 9
FLEX(1) FLEX(1)
If no match is found, then the default rule is executed:
the next character in the input is considered matched and
copied to the standard output. Thus, the simplest legal
flex input is:
%%
which generates a scanner that simply copies its input
(one character at a time) to its output.
Note that yytext can be defined in two different ways:
either as a character pointer or as a character array.
You can control which definition flex uses by including
one of the special directives %pointer or %array in the
first (definitions) section of your flex input. The
default is %pointer, unless you use the -l lex compatibil-
ity option, in which case yytext will be an array. The
advantage of using %pointer is substantially faster scan-
ning and no buffer overflow when matching very large
tokens (unless you run out of dynamic memory). The disad-
vantage is that you are restricted in how your actions can
modify yytext (see the next section), and calls to the
unput() function destroys the present contents of yytext,
which can be a considerable porting headache when moving
between different lex versions.
The advantage of %array is that you can then modify yytext
to your heart's content, and calls to unput() do not
destroy yytext (see below). Furthermore, existing lex
programs sometimes access yytext externally using declara-
tions of the form:
extern char yytext[];
This definition is erroneous when used with %pointer, but
correct for %array.
%array defines yytext to be an array of YYLMAX characters,
which defaults to a fairly large value. You can change
the size by simply #define'ing YYLMAX to a different value
in the first section of your flex input. As mentioned
above, with %pointer yytext grows dynamically to accommo-
date large tokens. While this means your %pointer scanner
can accommodate very large tokens (such as matching entire
blocks of comments), bear in mind that each time the scan-
ner must resize yytext it also must rescan the entire
token from the beginning, so matching such tokens can
prove slow. yytext presently does not dynamically grow if
a call to unput() results in too much text being pushed
back; instead, a run-time error results.
Also note that you cannot use %array with C++ scanner
classes (the c++ option; see below).
ACTIONS
Each pattern in a rule has a corresponding action, which
Version 2.5 April 1995 10
FLEX(1) FLEX(1)
can be any arbitrary C statement. The pattern ends at the
first non-escaped whitespace character; the remainder of
the line is its action. If the action is empty, then when
the pattern is matched the input token is simply dis-
carded. For example, here is the specification for a pro-
gram which deletes all occurrences of "zap me" from its
input:
%%
"zap me"
(It will copy all other characters in the input to the
output since they will be matched by the default rule.)
Here is a program which compresses multiple blanks and
tabs down to a single blank, and throws away whitespace
found at the end of a line:
%%
[ \t]+ putchar( ' ' );
[ \t]+$ /* ignore this token */
If the action contains a '{', then the action spans till
the balancing '}' is found, and the action may cross mul-
tiple lines. flex knows about C strings and comments and
won't be fooled by braces found within them, but also
allows actions to begin with %{ and will consider the
action to be all the text up to the next %} (regardless of
ordinary braces inside the action).
An action consisting solely of a vertical bar ('|') means
"same as the action for the next rule." See below for an
illustration.
Actions can include arbitrary C code, including return
statements to return a value to whatever routine called
yylex(). Each time yylex() is called it continues pro-
cessing tokens from where it last left off until it either
reaches the end of the file or executes a return.
Actions are free to modify yytext except for lengthening
it (adding characters to its end--these will overwrite
later characters in the input stream). This however does
not apply when using %array (see above); in that case,
yytext may be freely modified in any way.
Actions are free to modify yyleng except they should not
do so if the action also includes use of yymore() (see
below).
There are a number of special directives which can be
included within an action:
Version 2.5 April 1995 11
FLEX(1) FLEX(1)
- ECHO copies yytext to the scanner's output.
- BEGIN followed by the name of a start condition
places the scanner in the corresponding start con-
dition (see below).
- REJECT directs the scanner to proceed on to the
"second best" rule which matched the input (or a
prefix of the input). The rule is chosen as
described above in "How the Input is Matched", and
yytext and yyleng set up appropriately. It may
either be one which matched as much text as the
originally chosen rule but came later in the flex
input file, or one which matched less text. For
example, the following will both count the words in
the input and call the routine special() whenever
"frob" is seen:
int word_count = 0;
%%
frob special(); REJECT;
[^ \t\n]+ ++word_count;
Without the REJECT, any "frob"'s in the input would
not be counted as words, since the scanner normally
executes only one action per token. Multiple
REJECT's are allowed, each one finding the next
best choice to the currently active rule. For
example, when the following scanner scans the token
"abcd", it will write "abcdabcaba" to the output:
%%
a |
ab |
abc |
abcd ECHO; REJECT;
.|\n /* eat up any unmatched character */
(The first three rules share the fourth's action
since they use the special '|' action.) REJECT is
a particularly expensive feature in terms of scan-
ner performance; if it is used in any of the scan-
ner's actions it will slow down all of the scan-
ner's matching. Furthermore, REJECT cannot be used
with the -Cf or -CF options (see below).
Note also that unlike the other special actions,
REJECT is a branch; code immediately following it
in the action will not be executed.
- yymore() tells the scanner that the next time it
matches a rule, the corresponding token should be
appended onto the current value of yytext rather
Version 2.5 April 1995 12
FLEX(1) FLEX(1)
than replacing it. For example, given the input
"mega-kludge" the following will write "mega-mega-
kludge" to the output:
%%
mega- ECHO; yymore();
kludge ECHO;
First "mega-" is matched and echoed to the output.
Then "kludge" is matched, but the previous "mega-"
is still hanging around at the beginning of yytext
so the ECHO for the "kludge" rule will actually
write "mega-kludge".
Two notes regarding use of yymore(). First, yymore()
depends on the value of yyleng correctly reflecting the
size of the current token, so you must not modify yyleng
if you are using yymore(). Second, the presence of
yymore() in the scanner's action entails a minor perfor-
mance penalty in the scanner's matching speed.
- yyless(n) returns all but the first n characters of
the current token back to the input stream, where
they will be rescanned when the scanner looks for
the next match. yytext and yyleng are adjusted
appropriately (e.g., yyleng will now be equal to n
). For example, on the input "foobar" the follow-
ing will write out "foobarbar":
%%
foobar ECHO; yyless(3);
[a-z]+ ECHO;
An argument of 0 to yyless will cause the entire
current input string to be scanned again. Unless
you've changed how the scanner will subsequently
process its input (using BEGIN, for example), this
will result in an endless loop.
Note that yyless is a macro and can only be used in the
flex input file, not from other source files.
- unput(c) puts the character c back onto the input
stream. It will be the next character scanned.
The following action will take the current token
and cause it to be rescanned enclosed in parenthe-
ses.
{
int i;
/* Copy yytext because unput() trashes yytext */
char *yycopy = strdup( yytext );
unput( ')' );
for ( i = yyleng - 1; i >= 0; --i )
Version 2.5 April 1995 13
FLEX(1) FLEX(1)
unput( yycopy[i] );
unput( '(' );
free( yycopy );
}
Note that since each unput() puts the given charac-
ter back at the beginning of the input stream,
pushing back strings must be done back-to-front.
An important potential problem when using unput() is that
if you are using %pointer (the default), a call to unput()
destroys the contents of yytext, starting with its right-
most character and devouring one character to the left
with each call. If you need the value of yytext preserved
after a call to unput() (as in the above example), you
must either first copy it elsewhere, or build your scanner
using %array instead (see How The Input Is Matched).
Finally, note that you cannot put back EOF to attempt to
mark the input stream with an end-of-file.
- input() reads the next character from the input
stream. For example, the following is one way to
eat up C comments:
%%
"/*" {
register int c;
for ( ; ; )
{
while ( (c = input()) != '*' &&
c != EOF )
; /* eat up text of comment */
if ( c == '*' )
{
while ( (c = input()) == '*' )
;
if ( c == '/' )
break; /* found the end */
}
if ( c == EOF )
{
error( "EOF in comment" );
break;
}
}
}
(Note that if the scanner is compiled using C++,
then input() is instead referred to as yyinput(),
in order to avoid a name clash with the C++ stream
Version 2.5 April 1995 14
FLEX(1) FLEX(1)
by the name of input.)
- YY_FLUSH_BUFFER flushes the scanner's internal
buffer so that the next time the scanner attempts
to match a token, it will first refill the buffer
using YY_INPUT (see The Generated Scanner, below).
This action is a special case of the more general
yy_flush_buffer() function, described below in the
section Multiple Input Buffers.
- yyterminate() can be used in lieu of a return
statement in an action. It terminates the scanner
and returns a 0 to the scanner's caller, indicating
"all done". By default, yyterminate() is also
called when an end-of-file is encountered. It is a
macro and may be redefined.
THE GENERATED SCANNER
The output of flex is the file //ddn:lexyyc which contains
the scanning routine yylex(), a number of tables used by
it for matching tokens, and a number of auxiliary routines
and macros. By default, yylex() is declared as follows:
int yylex()
{
... various definitions and the actions in here ...
}
(If your environment supports function prototypes, then it
will be "int yylex( void )".) This definition may be
changed by defining the "YY_DECL" macro. For example, you
could use:
#define YY_DECL float lexscan( a, b ) float a, b;
to give the scanning routine the name lexscan, returning a
float, and taking two floats as arguments. Note that if
you give arguments to the scanning routine using a K&R-
style/non-prototyped function declaration, you must termi-
nate the definition with a semi-colon (;).
Whenever yylex() is called, it scans tokens from the
global input file yyin (which defaults to stdin). It con-
tinues until it either reaches an end-of-file (at which
point it returns the value 0) or one of its actions exe-
cutes a return statement.
If the scanner reaches an end-of-file, subsequent calls
are undefined unless either yyin is pointed at a new input
file (in which case scanning continues from that file), or
yyrestart() is called. yyrestart() takes one argument, a
FILE * pointer (which can be nil, if you've set up
YY_INPUT to scan from a source other than yyin), and ini-
tializes yyin for scanning from that file. Essentially
Version 2.5 April 1995 15
FLEX(1) FLEX(1)
there is no difference between just assigning yyin to a
new input file or using yyrestart() to do so; the latter
is available for compatibility with previous versions of
flex, and because it can be used to switch input files in
the middle of scanning. It can also be used to throw away
the current input buffer, by calling it with an argument
of yyin; but better is to use YY_FLUSH_BUFFER (see above).
Note that yyrestart() does not reset the start condition
to INITIAL (see Start Conditions, below).
If yylex() stops scanning due to executing a return state-
ment in one of the actions, the scanner may then be called
again and it will resume scanning where it left off.
By default (and for purposes of efficiency), the scanner
uses block-reads rather than simple getc() calls to read
characters from yyin. The nature of how it gets its input
can be controlled by defining the YY_INPUT macro.
YY_INPUT's calling sequence is
"YY_INPUT(buf,result,max_size)". Its action is to place
up to max_size characters in the character array buf and
return in the integer variable result either the number of
characters read or the constant YY_NULL (0 on Unix sys-
tems) to indicate EOF. The default YY_INPUT reads from
the global file-pointer "yyin".
A sample definition of YY_INPUT (in the definitions sec-
tion of the input file):
%{
#define YY_INPUT(buf,result,max_size) \
{ \
int c = getchar(); \
result = (c == EOF) ? YY_NULL : (buf[0] = c, 1); \
}
%}
This definition will change the input processing to occur
one character at a time.
When the scanner receives an end-of-file indication from
YY_INPUT, it then checks the yywrap() function. If
yywrap() returns false (zero), then it is assumed that the
function has gone ahead and set up yyin to point to
another input file, and scanning continues. If it returns
true (non-zero), then the scanner terminates, returning 0
to its caller. Note that in either case, the start condi-
tion remains unchanged; it does not revert to INITIAL.
If you do not supply your own version of yywrap(), then
you must either use %option noyywrap (in which case the
scanner behaves as though yywrap() returned 1), or you
must link with -lfl to obtain the default version of the
routine, which always returns 1.
Version 2.5 April 1995 16
FLEX(1) FLEX(1)
Three routines are available for scanning from in-memory
buffers rather than files: yy_scan_string(),
yy_scan_bytes(), and yy_scan_buffer(). See the discussion
of them below in the section Multiple Input Buffers.
The scanner writes its ECHO output to the yyout global
(default, stdout), which may be redefined by the user sim-
ply by assigning it to some other FILE pointer.
START CONDITIONS
flex provides a mechanism for conditionally activating
rules. Any rule whose pattern is prefixed with "<sc>"
will only be active when the scanner is in the start con-
dition named "sc". For example,
<STRING>[^"]* { /* eat up the string body ... */
...
}
will be active only when the scanner is in the "STRING"
start condition, and
<INITIAL,STRING,QUOTE>\. { /* handle an escape ... */
...
}
will be active only when the current start condition is
either "INITIAL", "STRING", or "QUOTE".
Start conditions are declared in the definitions (first)
section of the input using unindented lines beginning with
either %s or %x followed by a list of names. The former
declares inclusive start conditions, the latter exclusive
start conditions. A start condition is activated using
the BEGIN action. Until the next BEGIN action is exe-
cuted, rules with the given start condition will be active
and rules with other start conditions will be inactive.
If the start condition is inclusive, then rules with no
start conditions at all will also be active. If it is
exclusive, then only rules qualified with the start condi-
tion will be active. A set of rules contingent on the
same exclusive start condition describe a scanner which is
independent of any of the other rules in the flex input.
Because of this, exclusive start conditions make it easy
to specify "mini-scanners" which scan portions of the
input that are syntactically different from the rest
(e.g., comments).
If the distinction between inclusive and exclusive start
conditions is still a little vague, here's a simple exam-
ple illustrating the connection between the two. The set
of rules:
%s example
Version 2.5 April 1995 17
FLEX(1) FLEX(1)
%%
<example>foo do_something();
bar something_else();
is equivalent to
%x example
%%
<example>foo do_something();
<INITIAL,example>bar something_else();
Without the <INITIAL,example> qualifier, the bar pattern
in the second example wouldn't be active (i.e., couldn't
match) when in start condition example. If we just used
<example> to qualify bar, though, then it would only be
active in example and not in INITIAL, while in the first
example it's active in both, because in the first example
the example startion condition is an inclusive (%s) start
condition.
Also note that the special start-condition specifier <*>
matches every start condition. Thus, the above example
could also have been written;
%x example
%%
<example>foo do_something();
<*>bar something_else();
The default rule (to ECHO any unmatched character) remains
active in start conditions. It is equivalent to:
<*>.|\n ECHO;
BEGIN(0) returns to the original state where only the
rules with no start conditions are active. This state can
also be referred to as the start-condition "INITIAL", so
BEGIN(INITIAL) is equivalent to BEGIN(0). (The parenthe-
ses around the start condition name are not required but
are considered good style.)
BEGIN actions can also be given as indented code at the
beginning of the rules section. For example, the follow-
ing will cause the scanner to enter the "SPECIAL" start
condition whenever yylex() is called and the global vari-
able enter_special is true:
Version 2.5 April 1995 18
FLEX(1) FLEX(1)
int enter_special;
%x SPECIAL
%%
if ( enter_special )
BEGIN(SPECIAL);
<SPECIAL>blahblahblah
...more rules follow...
To illustrate the uses of start conditions, here is a
scanner which provides two different interpretations of a
string like "123.456". By default it will treat it as
three tokens, the integer "123", a dot ('.'), and the
integer "456". But if the string is preceded earlier in
the line by the string "expect-floats" it will treat it as
a single token, the floating-point number 123.456:
%{
#include <math.h>
%}
%s expect
%%
expect-floats BEGIN(expect);
<expect>[0-9]+"."[0-9]+ {
printf( "found a float, = %f\n",
atof( yytext ) );
}
<expect>\n {
/* that's the end of the line, so
* we need another "expect-number"
* before we'll recognize any more
* numbers
*/
BEGIN(INITIAL);
}
[0-9]+ {
printf( "found an integer, = %d\n",
atoi( yytext ) );
}
"." printf( "found a dot\n" );
Here is a scanner which recognizes (and discards) C com-
ments while maintaining a count of the current input line.
%x comment
%%
int line_num = 1;
Version 2.5 April 1995 19
FLEX(1) FLEX(1)
"/*" BEGIN(comment);
<comment>[^*\n]* /* eat anything that's not a '*' */
<comment>"*"+[^*/\n]* /* eat up '*'s not followed by '/'s */
<comment>\n ++line_num;
<comment>"*"+"/" BEGIN(INITIAL);
This scanner goes to a bit of trouble to match as much
text as possible with each rule. In general, when
attempting to write a high-speed scanner try to match as
much possible in each rule, as it's a big win.
Note that start-conditions names are really integer values
and can be stored as such. Thus, the above could be
extended in the following fashion:
%x comment foo
%%
int line_num = 1;
int comment_caller;
"/*" {
comment_caller = INITIAL;
BEGIN(comment);
}
...
<foo>"/*" {
comment_caller = foo;
BEGIN(comment);
}
<comment>[^*\n]* /* eat anything that's not a '*' */
<comment>"*"+[^*/\n]* /* eat up '*'s not followed by '/'s */
<comment>\n ++line_num;
<comment>"*"+"/" BEGIN(comment_caller);
Furthermore, you can access the current start condition
using the integer-valued YY_START macro. For example, the
above assignments to comment_caller could instead be writ-
ten
comment_caller = YY_START;
Flex provides YYSTATE as an alias for YY_START (since that
is what's used by AT&T lex).
Note that start conditions do not have their own name-
space; %s's and %x's declare names in the same fashion as
#define's.
Finally, here's an example of how to match C-style quoted
strings using exclusive start conditions, including
Version 2.5 April 1995 20
FLEX(1) FLEX(1)
expanded escape sequences (but not including checking for
a string that's too long):
%x str
%%
char string_buf[MAX_STR_CONST];
char *string_buf_ptr;
\" string_buf_ptr = string_buf; BEGIN(str);
<str>\" { /* saw closing quote - all done */
BEGIN(INITIAL);
*string_buf_ptr = '\0';
/* return string constant token type and
* value to parser
*/
}
<str>\n {
/* error - unterminated string constant */
/* generate error message */
}
<str>\\[0-7]{1,3} {
/* octal escape sequence */
int result;
(void) sscanf( yytext + 1, "%o", &result );
if ( result > 0xff )
/* error, constant is out-of-bounds */
*string_buf_ptr++ = result;
}
<str>\\[0-9]+ {
/* generate error - bad escape sequence; something
* like '\48' or '\0777777'
*/
}
gt;\\n *string_buf_ptr++ = '\n';
gt;\\t *string_buf_ptr++ = '\t';
gt;\\r *string_buf_ptr++ = '\r';
gt;\\b *string_buf_ptr++ = '\b';
gt;\\f *string_buf_ptr++ = '\f';
gt;\\(.|\n) *string_buf_ptr++ = yytext[1];
gt;[^\\\n\"]+ {
char *yptr = yytext;
Version 2.5 April 1995 21
FLEX(1) FLEX(1)
while ( *yptr )
*string_buf_ptr++ = *yptr++;
}
Often, such as in some of the examples above, you wind up
writing a whole bunch of rules all preceded by the same
start condition(s). Flex makes this a little easier and
cleaner by introducing a notion of start condition scope.
A start condition scope is begun with:
gt;{
where SCs is a list of one or more start conditions.
Inside the start condition scope, every rule automatically
has the prefix gt; applied to it, until a '}' which
matches the initial '{'. So, for example,
gt;{
"\\n" return '\n';
"\\r" return '\r';
"\\f" return '\f';
"\\0" return '\0';
}
is equivalent to:
gt;"\\n" return '\n';
gt;"\\r" return '\r';
gt;"\\f" return '\f';
gt;"\\0" return '\0';
Start condition scopes may be nested.
Three routines are available for manipulating stacks of
start conditions:
void yy_push_state(int new_state)
pushes the current start condition onto the top of
the start condition stack and switches to new_state
as though you had used BEGIN new_state (recall that
start condition names are also integers).
void yy_pop_state()
pops the top of the stack and switches to it via
BEGIN.
int yy_top_state()
returns the top of the stack without altering the
stack's contents.
The start condition stack grows dynamically and so has no
built-in size limitation. If memory is exhausted, program
execution aborts.
Version 2.5 April 1995 22
FLEX(1) FLEX(1)
To use start condition stacks, your scanner must include a
%option stack directive (see Options below).
MULTIPLE INPUT BUFFERS
Some scanners (such as those which support "include"
files) require reading from several input streams. As
flex scanners do a large amount of buffering, one cannot
control where the next input will be read from by simply
writing a YY_INPUT which is sensitive to the scanning con-
text. YY_INPUT is only called when the scanner reaches
the end of its buffer, which may be a long time after
scanning a statement such as an "include" which requires
switching the input source.
To negotiate these sorts of problems, flex provides a
mechanism for creating and switching between multiple
input buffers. An input buffer is created by using:
YY_BUFFER_STATE yy_create_buffer( FILE *file, int size )
which takes a FILE pointer and a size and creates a buffer
associated with the given file and large enough to hold
size characters (when in doubt, use YY_BUF_SIZE for the
size). It returns a YY_BUFFER_STATE handle, which may
then be passed to other routines (see below). The
YY_BUFFER_STATE type is a pointer to an opaque struct
yy_buffer_state structure, so you may safely initialize
YY_BUFFER_STATE variables to ((YY_BUFFER_STATE) 0) if you
wish, and also refer to the opaque structure in order to
correctly declare input buffers in source files other than
that of your scanner. Note that the FILE pointer in the
call to yy_create_buffer is only used as the value of yyin
seen by YY_INPUT; if you redefine YY_INPUT so it no longer
uses yyin, then you can safely pass a nil FILE pointer to
yy_create_buffer. You select a particular buffer to scan
from using:
void yy_switch_to_buffer( YY_BUFFER_STATE new_buffer )
switches the scanner's input buffer so subsequent tokens
will come from new_buffer. Note that
yy_switch_to_buffer() may be used by yywrap() to set
things up for continued scanning, instead of opening a new
file and pointing yyin at it. Note also that switching
input sources via either yy_switch_to_buffer() or yywrap()
does not change the start condition.
void yy_delete_buffer( YY_BUFFER_STATE buffer )
is used to reclaim the storage associated with a buffer.
( buffer can be nil, in which case the routine does noth-
ing.) You can also clear the current contents of a buffer
using:
Version 2.5 April 1995 23
FLEX(1) FLEX(1)
void yy_flush_buffer( YY_BUFFER_STATE buffer )
This function discards the buffer's contents, so the next
time the scanner attempts to match a token from the
buffer, it will first fill the buffer anew using YY_INPUT.
yy_new_buffer() is an alias for yy_create_buffer(), pro-
vided for compatibility with the C++ use of new and delete
for creating and destroying dynamic objects.
Finally, the YY_CURRENT_BUFFER macro returns a
YY_BUFFER_STATE handle to the current buffer.
Here is an example of using these features for writing a
scanner which expands include files (the gt;>gt; feature
is discussed below):
/* the "incl" state is used for picking up the name
* of an include file
*/
%x incl
%{
#define MAX_INCLUDE_DEPTH 10
YY_BUFFER_STATE include_stack[MAX_INCLUDE_DEPTH];
int include_stack_ptr = 0;
%}
%%
include BEGIN(incl);
[a-z]+ ECHO;
[^a-z\n]*\n? ECHO;
gt;[ \t]* /* eat the whitespace */
gt;[^ \t\n]+ { /* got the include file name */
if ( include_stack_ptr >gt;= MAX_INCLUDE_DEPTH )
{
fprintf( stderr, "Includes nested too deeply" );
exit( 1 );
}
include_stack[include_stack_ptr++] =
YY_CURRENT_BUFFER;
yyin = fopen( yytext, "r" );
if ( ! yyin )
error( ... );
yy_switch_to_buffer(
yy_create_buffer( yyin, YY_BUF_SIZE ) );
BEGIN(INITIAL);
Version 2.5 April 1995 24
FLEX(1) FLEX(1)
}
gt;>gt; {
if ( --include_stack_ptr gt;>gt;" indicates actions which are to
be taken when an end-of-file is encountered and yywrap()
returns non-zero (i.e., indicates no further files to pro-
cess). The action must finish by doing one of four
things:
- assigning yyin to a new input file (in previous
versions of flex, after doing the assignment you
had to call the special action YY_NEW_FILE; this is
no longer necessary);
- executing a return statement;
- executing the special yyterminate() action;
- or, switching to a new buffer using
yy_switch_to_buffer() as shown in the example
above.
gt;>gt; rules may not be used with other patterns; they
may only be qualified with a list of start conditions. If
an unqualified gt;>gt; rule is given, it applies to all
start conditions which do not already have gt;>gt;
actions. To specify an gt;>gt; rule for only the initial
start condition, use
gt;gt;>gt;
These rules are useful for catching things like unclosed
comments. An example:
%x quote
%%
...other rules for dealing with quotes...
gt;gt;>gt; {
error( "unterminated quote" );
yyterminate();
}
gt;>gt; {
if ( *++filelist )
yyin = fopen( *filelist, "r" );
else
yyterminate();
}
MISCELLANEOUS MACROS
The macro YY_USER_ACTION can be defined to provide an
action which is always executed prior to the matched
rule's action. For example, it could be #define'd to call
Version 2.5 April 1995 26
FLEX(1) FLEX(1)
a routine to convert yytext to lower-case. When
YY_USER_ACTION is invoked, the variable yy_act gives the
number of the matched rule (rules are numbered starting
with 1). Suppose you want to profile how often each of
your rules is matched. The following would do the trick:
#define YY_USER_ACTION ++ctr[yy_act]
where ctr is an array to hold the counts for the different
rules. Note that the macro YY_NUM_RULES gives the total
number of rules (including the default rule, even if you
use -s), so a correct declaration for ctr is:
int ctr[YY_NUM_RULES];
The macro YY_USER_INIT may be defined to provide an action
which is always executed before the first scan (and before
the scanner's internal initializations are done). For
example, it could be used to call a routine to read in a
data table or open a logging file.
The macro yy_set_interactive(is_interactive) can be used
to control whether the current buffer is considered inter-
active. An interactive buffer is processed more slowly,
but must be used when the scanner's input source is indeed
interactive to avoid problems due to waiting to fill
buffers (see the discussion of the -I flag below). A non-
zero value in the macro invocation marks the buffer as
interactive, a zero value as non-interactive. Note that
use of this macro overrides %option always-interactive or
%option never-interactive (see Options below).
yy_set_interactive() must be invoked prior to beginning to
scan the buffer that is (or is not) to be considered
interactive.
The macro yy_set_bol(at_bol) can be used to control
whether the current buffer's scanning context for the next
token match is done as though at the beginning of a line.
A non-zero macro argument makes rules anchored with
The macro YY_AT_BOL() returns true if the next token
scanned from the current buffer will have '^' rules
active, false otherwise.
In the generated scanner, the actions are all gathered in
one large switch statement and separated using YY_BREAK,
which may be redefined. By default, it is simply a
"break", to separate each rule's action from the following
rule's. Redefining YY_BREAK allows, for example, C++
users to #define YY_BREAK to do nothing (while being very
careful that every rule ends with a "break" or a
"return"!) to avoid suffering from unreachable statement
warnings where because a rule's action ends with "return",
Version 2.5 April 1995 27
FLEX(1) FLEX(1)
the YY_BREAK is inaccessible.
VALUES AVAILABLE TO THE USER
This section summarizes the various values available to
the user in the rule actions.
- char *yytext holds the text of the current token.
It may be modified but not lengthened (you cannot
append characters to the end).
If the special directive %array appears in the
first section of the scanner description, then
yytext is instead declared char yytext[YYLMAX],
where YYLMAX is a macro definition that you can
redefine in the first section if you don't like the
default value (generally 8KB). Using %array
results in somewhat slower scanners, but the value
of yytext becomes immune to calls to input() and
unput(), which potentially destroy its value when
yytext is a character pointer. The opposite of
%array is %pointer, which is the default.
You cannot use %array when generating C++ scanner
classes (the -+ flag).
- int yyleng holds the length of the current token.
- FILE *yyin is the file which by default flex reads
from. It may be redefined but doing so only makes
sense before scanning begins or after an EOF has
been encountered. Changing it in the midst of
scanning will have unexpected results since flex
buffers its input; use yyrestart() instead. Once
scanning terminates because an end-of-file has been
seen, you can assign yyin at the new input file and
then call the scanner again to continue scanning.
- void yyrestart( FILE *new_file ) may be called to
point yyin at the new input file. The switch-over
to the new file is immediate (any previously
buffered-up input is lost). Note that calling
yyrestart() with yyin as an argument thus throws
away the current input buffer and continues scan-
ning the same input file.
- FILE *yyout is the file to which ECHO actions are
done. It can be reassigned by the user.
- YY_CURRENT_BUFFER returns a YY_BUFFER_STATE handle
to the current buffer.
- YY_START returns an integer value corresponding to
the current start condition. You can subsequently
use this value with BEGIN to return to that start
Version 2.5 April 1995 28
FLEX(1) FLEX(1)
condition.
INTERFACING WITH YACC
One of the main uses of flex is as a companion to the yacc
parser-generator. yacc parsers expect to call a routine
named yylex() to find the next input token. The routine
is supposed to return the type of the next token as well
as putting any associated value in the global yylval. To
use flex with yacc, one specifies the -d option to yacc to
instruct it to generate the file y.tab.h containing defi-
nitions of all the %tokens appearing in the yacc input.
This file is then included in the flex scanner. For exam-
ple, if one of the tokens is "TOK_NUMBER", part of the
scanner might look like:
%{
#include "y.tab.h"
%}
%%
[0-9]+ yylval = atoi( yytext ); return TOK_NUMBER;
OPTIONS
flex has the following options:
-b Generate backing-up information to lex.backup.
This is a list of scanner states which require
backing up and the input characters on which they
do so. By adding rules one can remove backing-up
states. If all backing-up states are eliminated
and -Cf or -CF is used, the generated scanner will
run faster (see the -p flag). Only users who wish
to squeeze every last cycle out of their scanners
need worry about this option. (See the section on
Performance Considerations below.)
-c is a do-nothing, deprecated option included for
POSIX compliance.
-d makes the generated scanner run in debug mode.
Whenever a pattern is recognized and the global
yy_flex_debug is non-zero (which is the default),
the scanner will write to stderr a line of the
form:
--accepting rule at line 53 ("the matched text")
The line number refers to the location of the rule
in the file defining the scanner (i.e., the file
that was fed to flex). Messages are also generated
when the scanner backs up, accepts the default
rule, reaches the end of its input buffer (or
Version 2.5 April 1995 29
FLEX(1) FLEX(1)
encounters a NUL; at this point, the two look the
same as far as the scanner's concerned), or reaches
an end-of-file.
-f specifies fast scanner. No table compression is
done and stdio is bypassed. The result is large
but fast. This option is equivalent to -Cfr (see
below).
-h generates a "help" summary of flex's options to
stdout and then exits. -? and --help are synonyms
for -h.
-i instructs flex to generate a case-insensitive scan-
ner. The case of letters given in the flex input
patterns will be ignored, and tokens in the input
will be matched regardless of case. The matched
text given in yytext will have the preserved case
(i.e., it will not be folded).
-l turns on maximum compatibility with the original
AT&T lex implementation. Note that this does not
mean full compatibility. Use of this option costs
a considerable amount of performance, and it cannot
be used with the -+, -f, -F, -Cf, or -CF options.
For details on the compatibilities it provides, see
the section "Incompatibilities With Lex And POSIX"
below. This option also results in the name
YY_FLEX_LEX_COMPAT being #define'd in the generated
scanner.
-n is another do-nothing, deprecated option included
only for POSIX compliance.
-p generates a performance report to stderr. The
report consists of comments regarding features of
the flex input file which will cause a serious loss
of performance in the resulting scanner. If you
give the flag twice, you will also get comments
regarding features that lead to minor performance
losses.
Note that the use of REJECT, %option yylineno, and
variable trailing context (see the Deficiencies /
Bugs section below) entails a substantial perfor-
mance penalty; use of yymore(), the ^ operator, and
the -I flag entail minor performance penalties.
-s causes the default rule (that unmatched scanner
input is echoed to stdout) to be suppressed. If
the scanner encounters input that does not match
any of its rules, it aborts with an error. This
option is useful for finding holes in a scanner's
rule set.
Version 2.5 April 1995 30
FLEX(1) FLEX(1)
-t instructs flex to write the scanner it generates to
standard output instead of //ddn:lexyyc.
-v specifies that flex should write to stderr a sum-
mary of statistics regarding the scanner it gener-
ates. Most of the statistics are meaningless to
the casual flex user, but the first line identifies
the version of flex (same as reported by -V), and
the next line the flags used when generating the
scanner, including those that are on by default.
-w suppresses warning messages.
-B instructs flex to generate a batch scanner, the
opposite of interactive scanners generated by -I
(see below). In general, you use -B when you are
certain that your scanner will never be used inter-
actively, and you want to squeeze a little more
performance out of it. If your goal is instead to
squeeze out a lot more performance, you should be
using the -Cf or -CF options (discussed below),
which turn on -B automatically anyway.
-F specifies that the fast scanner table representa-
tion should be used (and stdio bypassed). This
representation is about as fast as the full table
representation (-f), and for some sets of patterns
will be considerably smaller (and for others,
larger). In general, if the pattern set contains
both "keywords" and a catch-all, "identifier" rule,
such as in the set:
"case" return TOK_CASE;
"switch" return TOK_SWITCH;
...
"default" return TOK_DEFAULT;
[a-z]+ return TOK_ID;
then you're better off using the full table repre-
sentation. If only the "identifier" rule is pre-
sent and you then use a hash table or some such to
detect the keywords, you're better off using -F.
This option is equivalent to -CFr (see below). It
cannot be used with -+.
-I instructs flex to generate an interactive scanner.
An interactive scanner is one that only looks ahead
to decide what token has been matched if it abso-
lutely must. It turns out that always looking one
extra character ahead, even if the scanner has
already seen enough text to disambiguate the cur-
rent token, is a bit faster than only looking ahead
when necessary. But scanners that always look
Version 2.5 April 1995 31
FLEX(1) FLEX(1)
ahead give dreadful interactive performance; for
example, when a user types a newline, it is not
recognized as a newline token until they enter
another token, which often means typing in another
whole line.
Flex scanners default to interactive unless you use
the -Cf or -CF table-compression options (see
below). That's because if you're looking for high-
performance you should be using one of these
options, so if you didn't, flex assumes you'd
rather trade off a bit of run-time performance for
intuitive interactive behavior. Note also that you
cannot use -I in conjunction with -Cf or -CF.
Thus, this option is not really needed; it is on by
default for all those cases in which it is allowed.
You can force a scanner to not be interactive by
using -B (see above).
-L instructs flex not to generate #line directives.
Without this option, flex peppers the generated
scanner with #line directives so error messages in
the actions will be correctly located with respect
to either the original flex input file (if the
errors are due to code in the input file), or
//ddn:lexyyc (if the errors are flex's fault -- you
should report these sorts of errors to the email
address given below).
-T makes flex run in trace mode. It will generate a
lot of messages to stderr concerning the form of
the input and the resultant non-deterministic and
deterministic finite automata. This option is
mostly for use in maintaining flex.
-V prints the version number to stdout and exits.
--version is a synonym for -V.
-7 instructs flex to generate a 7-bit scanner, i.e.,
one which can only recognized 7-bit characters in
its input. The advantage of using -7 is that the
scanner's tables can be up to half the size of
those generated using the -8 option (see below).
The disadvantage is that such scanners often hang
or crash if their input contains an 8-bit charac-
ter.
Note, however, that unless you generate your scan-
ner using the -Cf or -CF table compression options,
use of -7 will save only a small amount of table
space, and make your scanner considerably less
portable. Flex's default behavior is to generate
an 8-bit scanner unless you use the -Cf or -CF, in
Version 2.5 April 1995 32
FLEX(1) FLEX(1)
which case flex defaults to generating 7-bit scan-
ners unless your site was always configured to gen-
erate 8-bit scanners (as will often be the case
with non-USA sites). You can tell whether flex
generated a 7-bit or an 8-bit scanner by inspecting
the flag summary in the -v output as described
above.
Note that if you use -Cfe or -CFe (those table com-
pression options, but also using equivalence
classes as discussed see below), flex still
defaults to generating an 8-bit scanner, since usu-
ally with these compression options full 8-bit
tables are not much more expensive than 7-bit
tables.
-8 instructs flex to generate an 8-bit scanner, i.e.,
one which can recognize 8-bit characters. This
flag is only needed for scanners generated using
-Cf or -CF, as otherwise flex defaults to generat-
ing an 8-bit scanner anyway.
See the discussion of -7 above for flex's default
behavior and the tradeoffs between 7-bit and 8-bit
scanners.
-+ specifies that you want flex to generate a C++
scanner class. See the section on Generating C++
Scanners below for details.
-C[aefFmr]
controls the degree of table compression and, more
generally, trade-offs between small scanners and
fast scanners.
-Ca ("align") instructs flex to trade off larger
tables in the generated scanner for faster perfor-
mance because the elements of the tables are better
aligned for memory access and computation. On some
RISC architectures, fetching and manipulating long-
words is more efficient than with smaller-sized
units such as shortwords. This option can double
the size of the tables used by your scanner.
-Ce directs flex to construct equivalence classes,
i.e., sets of characters which have identical lexi-
cal properties (for example, if the only appearance
of digits in the flex input is in the character
class "[0-9]" then the digits '0', '1', ..., '9'
will all be put in the same equivalence class).
Equivalence classes usually give dramatic reduc-
tions in the final table/object file sizes (typi-
cally a factor of 2-5) and are pretty cheap perfor-
mance-wise (one array look-up per character
Version 2.5 April 1995 33
FLEX(1) FLEX(1)
scanned).
-Cf specifies that the full scanner tables should
be generated - flex should not compress the tables
by taking advantages of similar transition func-
tions for different states.
-CF specifies that the alternate fast scanner rep-
resentation (described above under the -F flag)
should be used. This option cannot be used with
-+.
-Cm directs flex to construct meta-equivalence
classes, which are sets of equivalence classes (or
characters, if equivalence classes are not being
used) that are commonly used together. Meta-equiv-
alence classes are often a big win when using com-
pressed tables, but they have a moderate perfor-
mance impact (one or two "if" tests and one array
look-up per character scanned).
-Cr causes the generated scanner to bypass use of
the standard I/O library (stdio) for input.
Instead of calling fread() or getc(), the scanner
will use the read() system call, resulting in a
performance gain which varies from system to sys-
tem, but in general is probably negligible unless
you are also using -Cf or -CF. Using -Cr can cause
strange behavior if, for example, you read from
yyin using stdio prior to calling the scanner
(because the scanner will miss whatever text your
previous reads left in the stdio input buffer).
-Cr has no effect if you define YY_INPUT (see The
Generated Scanner above).
A lone -C specifies that the scanner tables should
be compressed but neither equivalence classes nor
meta-equivalence classes should be used.
The options -Cf or -CF and -Cm do not make sense
together - there is no opportunity for meta-equiva-
lence classes if the table is not being compressed.
Otherwise the options may be freely mixed, and are
cumulative.
The default setting is -Cem, which specifies that
flex should generate equivalence classes and meta-
equivalence classes. This setting provides the
highest degree of table compression. You can trade
off faster-executing scanners at the cost of larger
tables with the following generally being true:
slowest & smallest
Version 2.5 April 1995 34
FLEX(1) FLEX(1)
-Cem
-Cm
-Ce
-C
-C{f,F}e
-C{f,F}
-C{f,F}a
fastest & largest
Note that scanners with the smallest tables are
usually generated and compiled the quickest, so
during development you will usually want to use the
default, maximal compression.
-Cfe is often a good compromise between speed and
size for production scanners.
-ooutput
directs flex to write the scanner to the file out-
put instead of //ddn:lexyyc. If you combine -o with
the -t option, then the scanner is written to std-
out but its #line directives (see the -L option
above) refer to the file output.
-Pprefix
changes the default yy prefix used by flex for all
globally-visible variable and function names to
instead be prefix. For example, -Pfoo changes the
name of yytext to footext. It also changes the
name of the default output file from //ddn:lexyyc
to //ddn:lexfooc. Here are all of the names
affected:
yy_create_buffer
yy_delete_buffer
yy_flex_debug
yy_init_buffer
yy_flush_buffer
yy_load_buffer_state
yy_switch_to_buffer
yyin
yyleng
yylex
yylineno
yyout
yyrestart
yytext
yywrap
(If you are using a C++ scanner, then only yywrap
and yyFlexLexer are affected.) Within your scanner
itself, you can still refer to the global variables
and functions using either version of their name;
but externally, they have the modified name.
Version 2.5 April 1995 35
FLEX(1) FLEX(1)
This option lets you easily link together multiple
flex programs into the same executable. Note,
though, that using this option also renames
yywrap(), so you now must either provide your own
(appropriately-named) version of the routine for
your scanner, or use %option noyywrap, as linking
with -lfl no longer provides one for you by
default.
-Sskeleton_file
overrides the default skeleton file from which flex
constructs its scanners. You'll never need this
option unless you are doing flex maintenance or
development.
flex also provides a mechanism for controlling options
within the scanner specification itself, rather than from
the flex command-line. This is done by including %option
directives in the first section of the scanner specifica-
tion. You can specify multiple options with a single
%option directive, and multiple directives in the first
section of your flex input file.
Most options are given simply as names, optionally pre-
ceded by the word "no" (with no intervening whitespace) to
negate their meaning. A number are equivalent to flex
flags or their negation:
7bit -7 option
8bit -8 option
align -Ca option
backup -b option
batch -B option
c++ -+ option
caseful or
case-sensitive opposite of -i (default)
case-insensitive or
caseless -i option
debug -d option
default opposite of -s option
ecs -Ce option
fast -F option
full -f option
interactive -I option
lex-compat -l option
meta-ecs -Cm option
perf-report -p option
read -Cr option
stdout -t option
verbose -v option
warn opposite of -w option
Version 2.5 April 1995 36
FLEX(1) FLEX(1)
(use "%option nowarn" for -w)
array equivalent to "%array"
pointer equivalent to "%pointer" (default)
Some %option's provide features otherwise not available:
always-interactive
instructs flex to generate a scanner which always
considers its input "interactive". Normally, on
each new input file the scanner calls isatty() in
an attempt to determine whether the scanner's input
source is interactive and thus should be read a
character at a time. When this option is used,
however, then no such call is made.
main directs flex to provide a default main() program
for the scanner, which simply calls yylex(). This
option implies noyywrap (see below).
never-interactive
instructs flex to generate a scanner which never
considers its input "interactive" (again, no call
made to isatty()). This is the opposite of always-
interactive.
stack enables the use of start condition stacks (see
Start Conditions above).
stdinit
if set (i.e., %option stdinit) initializes yyin and
yyout to stdin and stdout, instead of the default
of nil. Some existing lex programs depend on this
behavior, even though it is not compliant with ANSI
C, which does not require stdin and stdout to be
compile-time constant.
yylineno
directs flex to generate a scanner that maintains
the number of the current line read from its input
in the global variable yylineno. This option is
implied by %option lex-compat.
yywrap if unset (i.e., %option noyywrap), makes the scan-
ner not call yywrap() upon an end-of-file, but sim-
ply assume that there are no more files to scan
(until the user points yyin at a new file and calls
yylex() again).
flex scans your rule actions to determine whether you use
the REJECT or yymore() features. The reject and yymore
options are available to override its decision as to
whether you use the options, either by setting them (e.g.,
%option reject) to indicate the feature is indeed used, or
Version 2.5 April 1995 37
FLEX(1) FLEX(1)
unsetting them to indicate it actually is not used (e.g.,
%option noyymore).
Three options take string-delimited values, offset with
'=':
%option outfile="ABC"
is equivalent to -oABC, and
%option prefix="XYZ"
is equivalent to -PXYZ. Finally,
%option yyclass="foo"
only applies when generating a C++ scanner ( -+ option).
It informs flex that you have derived foo as a subclass of
yyFlexLexer, so flex will place your actions in the member
function foo::yylex() instead of yyFlexLexer::yylex(). It
also generates a yyFlexLexer::yylex() member function that
emits a run-time error (by invoking yyFlexLexer::Lexer-
Error()) if called. See Generating C++ Scanners, below,
for additional information.
A number of options are available for lint purists who
want to suppress the appearance of unneeded routines in
the generated scanner. Each of the following, if unset
(e.g., %option nounput ), results in the corresponding
routine not appearing in the generated scanner:
input, unput
yy_push_state, yy_pop_state, yy_top_state
yy_scan_buffer, yy_scan_bytes, yy_scan_string
(though yy_push_state() and friends won't appear anyway
unless you use %option stack).
PERFORMANCE CONSIDERATIONS
The main design goal of flex is that it generate high-per-
formance scanners. It has been optimized for dealing well
with large sets of rules. Aside from the effects on scan-
ner speed of the table compression -C options outlined
above, there are a number of options/actions which degrade
performance. These are, from most expensive to least:
REJECT
%option yylineno
arbitrary trailing context
pattern sets that require backing up
%array
%option interactive
%option always-interactive
Version 2.5 April 1995 38
FLEX(1) FLEX(1)
'^' beginning-of-line operator
yymore()
with the first three all being quite expensive and the
last two being quite cheap. Note also that unput() is
implemented as a routine call that potentially does quite
a bit of work, while yyless() is a quite-cheap macro; so
if just putting back some excess text you scanned, use
yyless().
REJECT should be avoided at all costs when performance is
important. It is a particularly expensive option.
Getting rid of backing up is messy and often may be an
enormous amount of work for a complicated scanner. In
principal, one begins by using the -b flag to generate a
lex.backup file. For example, on the input
%%
foo return TOK_KEYWORD;
foobar return TOK_KEYWORD;
the file looks like:
State #6 is non-accepting -
associated rule line numbers:
2 3
out-transitions: [ o ]
jam-transitions: EOF [ \001-n p-\177 ]
State #8 is non-accepting -
associated rule line numbers:
3
out-transitions: [ a ]
jam-transitions: EOF [ \001-` b-\177 ]
State #9 is non-accepting -
associated rule line numbers:
3
out-transitions: [ r ]
jam-transitions: EOF [ \001-q s-\177 ]
Compressed tables always back up.
The first few lines tell us that there's a scanner state
in which it can make a transition on an 'o' but not on any
other character, and that in that state the currently
scanned text does not match any rule. The state occurs
when trying to match the rules found at lines 2 and 3 in
the input file. If the scanner is in that state and then
reads something other than an 'o', it will have to back up
to find a rule which is matched. With a bit of head-
scratching one can see that this must be the state it's in
when it has seen "fo". When this has happened, if
Version 2.5 April 1995 39
FLEX(1) FLEX(1)
anything other than another 'o' is seen, the scanner will
have to back up to simply match the 'f' (by the default
rule).
The comment regarding State #8 indicates there's a problem
when "foob" has been scanned. Indeed, on any character
other than an 'a', the scanner will have to back up to
accept "foo". Similarly, the comment for State #9 con-
cerns when "fooba" has been scanned and an 'r' does not
follow.
The final comment reminds us that there's no point going
to all the trouble of removing backing up from the rules
unless we're using -Cf or -CF, since there's no perfor-
mance gain doing so with compressed scanners.
The way to remove the backing up is to add "error" rules:
%%
foo return TOK_KEYWORD;
foobar return TOK_KEYWORD;
fooba |
foob |
fo {
/* false alarm, not really a keyword */
return TOK_ID;
}
Eliminating backing up among a list of keywords can also
be done using a "catch-all" rule:
%%
foo return TOK_KEYWORD;
foobar return TOK_KEYWORD;
[a-z]+ return TOK_ID;
This is usually the best solution when appropriate.
Backing up messages tend to cascade. With a complicated
set of rules it's not uncommon to get hundreds of mes-
sages. If one can decipher them, though, it often only
takes a dozen or so rules to eliminate the backing up
(though it's easy to make a mistake and have an error rule
accidentally match a valid token. A possible future flex
feature will be to automatically add rules to eliminate
backing up).
It's important to keep in mind that you gain the benefits
of eliminating backing up only if you eliminate every
instance of backing up. Leaving just one means you gain
nothing.
Version 2.5 April 1995 40
FLEX(1) FLEX(1)
Variable trailing context (where both the leading and
trailing parts do not have a fixed length) entails almost
the same performance loss as REJECT (i.e., substantial).
So when possible a rule like:
%%
mouse|rat/(cat|dog) run();
is better written:
%%
mouse/cat|dog run();
rat/cat|dog run();
or as
%%
mouse|rat/cat run();
mouse|rat/dog run();
Note that here the special '|' action does not provide any
savings, and can even make things worse (see Deficiencies
/ Bugs below).
Another area where the user can increase a scanner's per-
formance (and one that's easier to implement) arises from
the fact that the longer the tokens matched, the faster
the scanner will run. This is because with long tokens
the processing of most input characters takes place in the
(short) inner scanning loop, and does not often have to go
through the additional work of setting up the scanning
environment (e.g., yytext) for the action. Recall the
scanner for C comments:
%x comment
%%
int line_num = 1;
"/*" BEGIN(comment);
gt;[^*\n]*
gt;"*"+[^*/\n]*
gt;\n ++line_num;
gt;"*"+"/" BEGIN(INITIAL);
This could be sped up by writing it as:
%x comment
%%
int line_num = 1;
"/*" BEGIN(comment);
gt;[^*\n]*
Version 2.5 April 1995 41
FLEX(1) FLEX(1)
gt;[^*\n]*\n ++line_num;
gt;"*"+[^*/\n]*
gt;"*"+[^*/\n]*\n ++line_num;
gt;"*"+"/" BEGIN(INITIAL);
Now instead of each newline requiring the processing of
another action, recognizing the newlines is "distributed"
over the other rules to keep the matched text as long as
possible. Note that adding rules does not slow down the
scanner! The speed of the scanner is independent of the
number of rules or (modulo the considerations given at the
beginning of this section) how complicated the rules are
with regard to operators such as '*' and '|'.
A final example in speeding up a scanner: suppose you want
to scan through a file containing identifiers and key-
words, one per line and with no other extraneous charac-
ters, and recognize all the keywords. A natural first
approach is:
%%
asm |
auto |
break |
... etc ...
volatile |
while /* it's a keyword */
.|\n /* it's not a keyword */
To eliminate the back-tracking, introduce a catch-all
rule:
%%
asm |
auto |
break |
... etc ...
volatile |
while /* it's a keyword */
[a-z]+ |
.|\n /* it's not a keyword */
Now, if it's guaranteed that there's exactly one word per
line, then we can reduce the total number of matches by a
half by merging in the recognition of newlines with that
of the other tokens:
%%
asm\n |
auto\n |
break\n |
... etc ...
Version 2.5 April 1995 42
FLEX(1) FLEX(1)
volatile\n |
while\n /* it's a keyword */
[a-z]+\n |
.|\n /* it's not a keyword */
One has to be careful here, as we have now reintroduced
backing up into the scanner. In particular, while we know
that there will never be any characters in the input
stream other than letters or newlines, flex can't figure
this out, and it will plan for possibly needing to back up
when it has scanned a token like "auto" and then the next
character is something other than a newline or a letter.
Previously it would then just match the "auto" rule and be
done, but now it has no "auto" rule, only a "auto\n" rule.
To eliminate the possibility of backing up, we could
either duplicate all rules but without final newlines, or,
since we never expect to encounter such an input and
therefore don't how it's classified, we can introduce one
more catch-all rule, this one which doesn't include a new-
line:
%%
asm\n |
auto\n |
break\n |
... etc ...
volatile\n |
while\n /* it's a keyword */
[a-z]+\n |
[a-z]+ |
.|\n /* it's not a keyword */
Compiled with -Cf, this is about as fast as one can get a
flex scanner to go for this particular problem.
A final note: flex is slow when matching NUL's, particu-
larly when a token contains multiple NUL's. It's best to
write rules which match short amounts of text if it's
anticipated that the text will often include NUL's.
Another final note regarding performance: as mentioned
above in the section How the Input is Matched, dynamically
resizing yytext to accommodate huge tokens is a slow pro-
cess because it presently requires that the (huge) token
be rescanned from the beginning. Thus if performance is
vital, you should attempt to match "large" quantities of
text but not "huge" quantities, where the cutoff between
the two is at about 8K characters/token.
GENERATING C++ SCANNERS
flex provides two different ways to generate scanners for
use with C++. The first way is to simply compile a
Version 2.5 April 1995 43
FLEX(1) FLEX(1)
scanner generated by flex using a C++ compiler instead of
a C compiler. You should not encounter any compilations
errors (please report any you find to the email address
given in the Author section below). You can then use C++
code in your rule actions instead of C code. Note that
the default input source for your scanner remains yyin,
and default echoing is still done to yyout. Both of these
remain FILE * variables and not C++ streams.
You can also use flex to generate a C++ scanner class,
using the -+ option (or, equivalently, %option c++), which
is automatically specified if the name of the flex exe-
cutable ends in a '+', such as flex++. When using this
option, flex defaults to generating the scanner to the
file //ddn:lexyycc instead of //ddn:lexyyc. The generated
scanner includes the header file FlexLexer.h, which
defines the interface to two C++ classes.
The first class, FlexLexer, provides an abstract base
class defining the general scanner class interface. It
provides the following member functions:
const char* YYText()
returns the text of the most recently matched
token, the equivalent of yytext.
int YYLeng()
returns the length of the most recently matched
token, the equivalent of yyleng.
int lineno() const
returns the current input line number (see %option
yylineno), or 1 if %option yylineno was not used.
void set_debug( int flag )
sets the debugging flag for the scanner, equivalent
to assigning to yy_flex_debug (see the Options sec-
tion above). Note that you must build the scanner
using %option debug to include debugging informa-
tion in it.
int debug() const
returns the current setting of the debugging flag.
Also provided are member functions equivalent to
yy_switch_to_buffer(), yy_create_buffer() (though the
first argument is an istream* object pointer and not a
FILE*), yy_flush_buffer(), yy_delete_buffer(), and
yyrestart() (again, the first argument is a istream*
object pointer).
The second class defined in FlexLexer.h is yyFlexLexer,
which is derived from FlexLexer. It defines the following
additional member functions:
Version 2.5 April 1995 44
FLEX(1) FLEX(1)
yyFlexLexer( istream* arg_yyin = 0, ostream* arg_yyout = 0
)
constructs a yyFlexLexer object using the given
streams for input and output. If not specified,
the streams default to cin and cout, respectively.
virtual int yylex()
performs the same role is yylex() does for ordinary
flex scanners: it scans the input stream, consuming
tokens, until a rule's action returns a value. If
you derive a subclass S from yyFlexLexer and want
to access the member functions and variables of S
inside yylex(), then you need to use %option
yyclass="S" to inform flex that you will be using
that subclass instead of yyFlexLexer. In this
case, rather than generating yyFlexLexer::yylex(),
flex generates S::yylex() (and also generates a
dummy yyFlexLexer::yylex() that calls
yyFlexLexer::LexerError() if called).
virtual void switch_streams(istream* new_in = 0,
ostream* new_out = 0) reassigns yyin to new_in (if
non-nil) and yyout to new_out (ditto), deleting the
previous input buffer if yyin is reassigned.
int yylex( istream* new_in, ostream* new_out = 0 )
first switches the input streams via
switch_streams( new_in, new_out ) and then returns
the value of yylex().
In addition, yyFlexLexer defines the following protected
virtual functions which you can redefine in derived
classes to tailor the scanner:
virtual int LexerInput( char* buf, int max_size )
reads up to max_size characters into buf and
returns the number of characters read. To indicate
end-of-input, return 0 characters. Note that
"interactive" scanners (see the -B and -I flags)
define the macro YY_INTERACTIVE. If you redefine
LexerInput() and need to take different actions
depending on whether or not the scanner might be
scanning an interactive input source, you can test
for the presence of this name via #ifdef.
virtual void LexerOutput( const char* buf, int size )
writes out size characters from the buffer buf,
which, while NUL-terminated, may also contain
"internal" NUL's if the scanner's rules can match
text with NUL's in them.
virtual void LexerError( const char* msg )
reports a fatal error message. The default version
of this function writes the message to the stream
Version 2.5 April 1995 45
FLEX(1) FLEX(1)
cerr and exits.
Note that a yyFlexLexer object contains its entire scan-
ning state. Thus you can use such objects to create reen-
trant scanners. You can instantiate multiple instances of
the same yyFlexLexer class, and you can also combine mul-
tiple C++ scanner classes together in the same program
using the -P option discussed above.
Finally, note that the %array feature is not available to
C++ scanner classes; you must use %pointer (the default).
Here is an example of a simple C++ scanner:
// An example of using the flex C++ scanner class.
%{
int mylineno = 0;
%}
string \"[^\n"]+\"
ws [ \t]+
alpha [A-Za-z]
dig [0-9]
name ({alpha}|{dig}|\$)({alpha}|{dig}|[_.\-/$])*
num1 [-+]?{dig}+\.?([eE][-+]?{dig}+)?
num2 [-+]?{dig}*\.{dig}+([eE][-+]?{dig}+)?
number {num1}|{num2}
%%
{ws} /* skip blanks and tabs */
"/*" {
int c;
while((c = yyinput()) != 0)
{
if(c == '\n')
++mylineno;
else if(c == '*')
{
if((c = yyinput()) == '/')
break;
else
unput(c);
}
}
}
{number} cout gt;yylex() != 0)
;
return 0;
}
If you want to create multiple (different) lexer classes,
you use the -P flag (or the prefix= option) to rename each
yyFlexLexer to some other xxFlexLexer. You then can
include gt; in your other sources once per lexer
class, first renaming yyFlexLexer as follows:
#undef yyFlexLexer
#define yyFlexLexer xxFlexLexer
#include gt;
#undef yyFlexLexer
#define yyFlexLexer zzFlexLexer
#include gt;
if, for example, you used %option prefix="xx" for one of
your scanners and %option prefix="zz" for the other.
IMPORTANT: the present form of the scanning class is
experimental and may change considerably between major
releases.
INCOMPATIBILITIES WITH LEX AND POSIX
flex is a rewrite of the AT&T Unix lex tool (the two
implementations do not share any code, though), with some
extensions and incompatibilities, both of which are of
concern to those who wish to write scanners acceptable to
either implementation. Flex is fully compliant with the
POSIX lex specification, except that when using %pointer
(the default), a call to unput() destroys the contents of
yytext, which is counter to the POSIX specification.
In this section we discuss all of the known areas of
incompatibility between flex, AT&T lex, and the POSIX
specification.
flex's -l option turns on maximum compatibility with the
original AT&T lex implementation, at the cost of a major
loss in the generated scanner's performance. We note
below which incompatibilities can be overcome using the -l
Version 2.5 April 1995 47
FLEX(1) FLEX(1)
option.
flex is fully compatible with lex with the following
exceptions:
- The undocumented lex scanner internal variable
yylineno is not supported unless -l or %option
yylineno is used.
yylineno should be maintained on a per-buffer
basis, rather than a per-scanner (single global
variable) basis.
yylineno is not part of the POSIX specification.
- The input() routine is not redefinable, though it
may be called to read characters following whatever
has been matched by a rule. If input() encounters
an end-of-file the normal yywrap() processing is
done. A ``real'' end-of-file is returned by
input() as EOF.
Input is instead controlled by defining the
YY_INPUT macro.
The flex restriction that input() cannot be rede-
fined is in accordance with the POSIX specifica-
tion, which simply does not specify any way of con-
trolling the scanner's input other than by making
an initial assignment to yyin.
- The unput() routine is not redefinable. This
restriction is in accordance with POSIX.
- flex scanners are not as reentrant as lex scanners.
In particular, if you have an interactive scanner
and an interrupt handler which long-jumps out of
the scanner, and the scanner is subsequently called
again, you may get the following message:
fatal flex scanner internal error--end of buffer missed
To reenter the scanner, first use
yyrestart( yyin );
Note that this call will throw away any buffered
input; usually this isn't a problem with an inter-
active scanner.
Also note that flex C++ scanner classes are reen-
trant, so if using C++ is an option for you, you
should use them instead. See "Generating C++ Scan-
ners" above for details.
Version 2.5 April 1995 48
FLEX(1) FLEX(1)
- output() is not supported. Output from the ECHO
macro is done to the file-pointer yyout (default
stdout).
output() is not part of the POSIX specification.
- lex does not support exclusive start conditions
(%x), though they are in the POSIX specification.
- When definitions are expanded, flex encloses them
in parentheses. With lex, the following:
NAME [A-Z][A-Z0-9]*
%%
foo{NAME}? printf( "Found it\n" );
%%
will not match the string "foo" because when the
macro is expanded the rule is equivalent to "foo[A-
Z][A-Z0-9]*?" and the precedence is such that the
'?' is associated with "[A-Z0-9]*". With flex, the
rule will be expanded to "foo([A-Z][A-Z0-9]*)?" and
so the string "foo" will match.
Note that if the definition begins with ^ or ends
with $ then it is not expanded with parentheses, to
allow these operators to appear in definitions
without losing their special meanings. But the
gt;, /, and gt;>gt; operators cannot be used in a
flex definition.
Using -l results in the lex behavior of no paren-
theses around the definition.
The POSIX specification is that the definition be
enclosed in parentheses.
- Some implementations of lex allow a rule's action
to begin on a separate line, if the rule's pattern
has trailing whitespace:
%%
foo|bargt;
{ foobar_action(); }
flex does not support this feature.
- The lex %r (generate a Ratfor scanner) option is
not supported. It is not part of the POSIX speci-
fication.
- After a call to unput(), yytext is undefined until
the next token is matched, unless the scanner was
built using %array. This is not the case with lex
Version 2.5 April 1995 49
FLEX(1) FLEX(1)
or the POSIX specification. The -l option does
away with this incompatibility.
- The precedence of the {} (numeric range) operator
is different. lex interprets "abc{1,3}" as "match
one, two, or three occurrences of 'abc'", whereas
flex interprets it as "match 'ab' followed by one,
two, or three occurrences of 'c'". The latter is
in agreement with the POSIX specification.
- The precedence of the ^ operator is different. lex
interprets "^foo|bar" as "match either 'foo' at the
beginning of a line, or 'bar' anywhere", whereas
flex interprets it as "match either 'foo' or 'bar'
if they come at the beginning of a line". The lat-
ter is in agreement with the POSIX specification.
- The special table-size declarations such as %a sup-
ported by lex are not required by flex scanners;
flex ignores them.
- The name FLEX_SCANNER is #define'd so scanners may
be written for use with either flex or lex. Scan-
ners also include YY_FLEX_MAJOR_VERSION and
YY_FLEX_MINOR_VERSION indicating which version of
flex generated the scanner (for example, for the
2.5 release, these defines would be 2 and 5 respec-
tively).
The following flex features are not included in lex or the
POSIX specification:
C++ scanners
%option
start condition scopes
start condition stacks
interactive/non-interactive scanners
yy_scan_string() and friends
yyterminate()
yy_set_interactive()
yy_set_bol()
YY_AT_BOL()
gt;>gt;
gt;
YY_DECL
YY_START
YY_USER_ACTION
YY_USER_INIT
#line directives
%{}'s around actions
multiple actions on a line
plus almost all of the flex flags. The last feature in
the list refers to the fact that with flex you can put
Version 2.5 April 1995 50
FLEX(1) FLEX(1)
multiple actions on the same line, separated with semi-
colons, while with lex, the following
foo handle_foo(); ++num_foos_seen;
is (rather surprisingly) truncated to
foo handle_foo();
flex does not truncate the action. Actions that are not
enclosed in braces are simply terminated at the end of the
line.
DIAGNOSTICS
warning, rule cannot be matched indicates that the given
rule cannot be matched because it follows other rules that
will always match the same text as it. For example, in
the following "foo" cannot be matched because it comes
after an identifier "catch-all" rule:
[a-z]+ got_identifier();
foo got_foo();
Using REJECT in a scanner suppresses this warning.
warning, -s option given but default rule can be matched
means that it is possible (perhaps only in a particular
start condition) that the default rule (match any single
character) is the only one that will match a particular
input. Since -s was given, presumably this is not
intended.
reject_used_but_not_detected undefined or
yymore_used_but_not_detected undefined - These errors can
occur at compile time. They indicate that the scanner
uses REJECT or yymore() but that flex failed to notice the
fact, meaning that flex scanned the first two sections
looking for occurrences of these actions and failed to
find any, but somehow you snuck some in (via a #include
file, for example). Use %option reject or %option yymore
to indicate to flex that you really do use these features.
flex scanner jammed - a scanner compiled with -s has
encountered an input string which wasn't matched by any of
its rules. This error can also occur due to internal
problems.
token too large, exceeds YYLMAX - your scanner uses %array
and one of its rules matched a string longer than the YYL-
MAX constant (8K bytes by default). You can increase the
value by #define'ing YYLMAX in the definitions section of
your flex input.
scanner requires -8 flag to use the character 'x' - Your
Version 2.5 April 1995 51
FLEX(1) FLEX(1)
scanner specification includes recognizing the 8-bit char-
acter 'x' and you did not specify the -8 flag, and your
scanner defaulted to 7-bit because you used the -Cf or -CF
table compression options. See the discussion of the -7
flag for details.
flex scanner push-back overflow - you used unput() to push
back so much text that the scanner's buffer could not hold
both the pushed-back text and the current token in yytext.
Ideally the scanner should dynamically resize the buffer
in this case, but at present it does not.
input buffer overflow, can't enlarge buffer because scan-
ner uses REJECT - the scanner was working on matching an
extremely large token and needed to expand the input
buffer. This doesn't work with scanners that use REJECT.
fatal flex scanner internal error--end of buffer missed -
This can occur in an scanner which is reentered after a
long-jump has jumped out (or over) the scanner's activa-
tion frame. Before reentering the scanner, use:
yyrestart( yyin );
or, as noted above, switch to using the C++ scanner class.
too many start conditions in gt; construct! - you listed
more start conditions in a gt; construct than exist (so you
must have listed at least one of them twice).
FILES
//ddn:lexyyc
generated scanner (called lexyy.c on some systems).
//ddn:lexyycc
generated C++ scanner class, when using -+.
<FlexLexer.h>
header file defining the C++ scanner base class,
FlexLexer, and its derived class, yyFlexLexer.
//ddn:lexbck
backing-up information for -b flag (called lex.bck
on some systems).
DEFICIENCIES / BUGS
Some trailing context patterns cannot be properly matched
and generate warning messages ("dangerous trailing
Version 2.5 April 1995 52
FLEX(1) FLEX(1)
context"). These are patterns where the ending of the
first part of the rule matches the beginning of the second
part, such as "zx*/xy*", where the 'x*' matches the 'x' at
the beginning of the trailing context. (Note that the
POSIX draft states that the text matched by such patterns
is undefined.)
For some trailing context rules, parts which are actually
fixed-length are not recognized as such, leading to the
abovementioned performance loss. In particular, parts
using '|' or {n} (such as "foo{3}") are always considered
variable-length.
Combining trailing context with the special '|' action can
result in fixed trailing context being turned into the
more expensive variable trailing context. For example, in
the following:
%%
abc |
xyz/def
Use of unput() invalidates yytext and yyleng, unless the
%array directive or the -l option has been used.
Pattern-matching of NUL's is substantially slower than
matching other characters.
Dynamic resizing of the input buffer is slow, as it
entails rescanning all the text matched so far by the cur-
rent (generally huge) token.
Due to both buffering of input and read-ahead, you cannot
intermix calls to gt; routines, such as, for exam-
ple, getchar(), with flex rules and expect it to work.
Call input() instead.
The total table entries listed by the -v flag excludes the
number of table entries needed to determine what rule has
been matched. The number of entries is equal to the num-
ber of DFA states if the scanner does not use REJECT, and
somewhat greater than the number of states if it does.
REJECT cannot be used with the -f or -F options.
The flex internal algorithms need documentation.
SEE ALSO
lex(1), yacc(1), sed(1), awk(1).
John Levine, Tony Mason, and Doug Brown, Lex & Yacc,
O'Reilly and Associates. Be sure to get the 2nd edition.
Version 2.5 April 1995 53
FLEX(1) FLEX(1)
M. E. Lesk and E. Schmidt, LEX - Lexical Analyzer Genera-
tor
Alfred Aho, Ravi Sethi and Jeffrey Ullman, Compilers:
Principles, Techniques and Tools, Addison-Wesley (1986).
Describes the pattern-matching techniques used by flex
(deterministic finite automata).
AUTHOR
Vern Paxson, with the help of many ideas and much inspira-
tion from Van Jacobson. Original version by Jef
Poskanzer. The fast table representation is a partial
implementation of a design done by Van Jacobson. The
implementation was done by Kevin Gong and Vern Paxson.
Thanks to the many flex beta-testers, feedbackers, and
contributors, especially Francois Pinard, Casey Leedom,
Robert Abramovitz, Stan Adermann, Terry Allen, David
Barker-Plummer, John Basrai, Neal Becker, Nelson H.F.
Beebe, benson@odi.com, Karl Berry, Peter A. Bigot, Simon
Blanchard, Keith Bostic, Frederic Brehm, Ian Brockbank,
Kin Cho, Nick Christopher, Brian Clapper, J.T. Conklin,
Jason Coughlin, Bill Cox, Nick Cropper, Dave Curtis, Scott
David Daniels, Chris G. Demetriou, Theo Deraadt, Mike Don-
ahue, Chuck Doucette, Tom Epperly, Leo Eskin, Chris Fay-
lor, Chris Flatters, Jon Forrest, Jeffrey Friedl, Joe
Gayda, Kaveh R. Ghazi, Wolfgang Glunz, Eric Goldman,
Christopher M. Gould, Ulrich Grepel, Peer Griebel, Jan
Hajic, Charles Hemphill, NORO Hideo, Jarkko Hietaniemi,
Scott Hofmann, Jeff Honig, Dana Hudes, Eric Hughes, John
Interrante, Ceriel Jacobs, Michal Jaegermann, Sakari Jalo-
vaara, Jeffrey R. Jones, Henry Juengst, Klaus Kaempf,
Jonathan I. Kamens, Terrence O Kane, Amir Katz,
ken@ken.hilco.com, Kevin B. Kenny, Steve Kirsch, Winfried
Koenig, Marq Kole, Ronald Lamprecht, Greg Lee, Rohan
Lenard, Craig Leres, John Levine, Steve Liddle, David Lof-
fredo, Mike Long, Mohamed el Lozy, Brian Madsen, Malte,
Joe Marshall, Bengt Martensson, Chris Metcalf, Luke Mew-
burn, Jim Meyering, R. Alexander Milowski, Erik Naggum,
G.T. Nicol, Landon Noll, James Nordby, Marc Nozell,
Richard Ohnemus, Karsten Pahnke, Sven Panne, Roland Pesch,
Walter Pelissero, Gaumond Pierre, Esmond Pitt, Jef
Poskanzer, Joe Rahmeh, Jarmo Raiha, Frederic Raimbault,
Pat Rankin, Rick Richardson, Kevin Rodgers, Kai Uwe Rom-
mel, Jim Roskind, Alberto Santini, Andreas Scherer, Dar-
rell Schiebel, Raf Schietekat, Doug Schmidt, Philippe Sch-
noebelen, Andreas Schwab, Larry Schwimmer, Alex Siegel,
Eckehard Stolz, Jan-Erik Strvmquist, Mike Stump, Paul Stu-
art, Dave Tallman, Ian Lance Taylor, Chris Thewalt,
Richard M. Timoney, Jodi Tsai, Paul Tuinenga, Gary Weik,
Frank Whaley, Gerhard Wilhelms, Kent Williams, Ken Yap,
Ron Zellar, Nathan Zelle, David Zuhn, and those whose
names have slipped my marginal mail-archiving skills but
whose contributions are appreciated all the same.
Version 2.5 April 1995 54
FLEX(1) FLEX(1)
Thanks to Keith Bostic, Jon Forrest, Noah Friedman, John
Gilmore, Craig Leres, John Levine, Bob Mulcahy, G.T.
Nicol, Francois Pinard, Rich Salz, and Richard Stallman
for help with various distribution headaches.
Thanks to Esmond Pitt and Earle Horton for 8-bit character
support; to Benson Margulies and Fred Burke for C++ sup-
port; to Kent Williams and Tom Epperly for C++ class sup-
port; to Ove Ewerlid for support of NUL's; and to Eric
Hughes for support of multiple buffers.
This work was primarily done when I was with the Real Time
Systems Group at the Lawrence Berkeley Laboratory in
Berkeley, CA. Many thanks to all there for the support I
received.
Send comments to vern@ee.lbl.gov.
Version 2.5 April 1995 55
Here's some sample JCL for running FLEX. In this example, //DDN:STDIN
is read to produce the generated lexer on //DDN:SOURCE. //DDN:SOURCE
can then be compiled by a C compiler (such as
Systems/C) and linked with
your program.
//FLEX JOB
//STEP1 EXEC PGM=FLEX,PARM='-o//DDN:SOURCE'
//STEPLIB DD DSN=flex.load.module,DISP=SHR
//SYSUDUMP DD SYSOUT=*
//SYSPRINT DD SYSOUT=*
//SYSTERM DD SYSOUT=*
//BFILE DD DSN=BFILE,LRECL=80,DISP=SHR
//STDOUT DD SYSOUT=*,LRECL=133,RECFM=FB
//STDERR DD SYSOUT=*,LRECL=133,RECFM=FB
//SOURCE DD SYSOUT=*,LRECL=133,RECFM=FB
//STDIN DD *,LRECL=80
... flex input ...
//
|
