CWEB(1) General Commands Manual CWEB(1)
NAME
ctangle, cweave - translate CWEB to C/C++ and/or TeX
SYNOPSIS
ctangle [options] webfile[.w] [{changefile[.ch]|-} [outfile[.c]]]
cweave [options] webfile[.w] [{changefile[.ch]|-} [outfile[.tex]]]
DESCRIPTION
The ctangle program converts a CWEB source document into a C/C++ program
that may be compiled in the usual way. The output file includes #line
specifications so that debugging can be done in terms of the CWEB source
file.
The cweave program converts the same CWEB file into a TeX file that may
be formatted and printed in the usual way. It takes appropriate care of
typographic details like page layout and the use of indentation, ital-
ics, boldface, etc., and it supplies extensive cross-index information
that it gathers automatically.
CWEB allows you to prepare a single document containing all the informa-
tion that is needed both to produce a compilable C/C++ program and to
produce a well-formatted document describing the program in as much de-
tail as the writer may desire. The user of CWEB ought to be familiar
with TeX as well as C/C++.
USAGE
The command line should have one, two, or three names on it. The first
is taken as the CWEB input file (and .w is added if there is no exten-
sion). If there is a second name, it is a change file (and .ch is added
if there is no extension). The change file overrides parts of the CWEB
file, as described in the documentation. If there is a third name, it
overrides the default name of the output file, which is ordinarily the
same as the name of the input file (but on the current directory) with
the extension .tex. If you just want to change the output file name,
but don’t have a change file to apply, you can use `-' as the second ar-
gument.
DIFFERENCES TO ORIGINAL CWEB
CWEBbin tries hard to be a drop-in replacement for CWEB, so in general
you should not notice any differences in invoking the programs nor in
the resulting output. There are, however, a few differences worth not-
ing:
• Options --help, --quiet, --verbose, --version, and flags +c, -i, -o,
+u, and +lX are new in CWEBbin and TeX Live.
• Option +lX is accompanied by several wrapper files for cwebmac.tex
with translated captions for German (+ld), French (+lf), and Italian
(+li).
• CWEB in TeX Live operates silently by default (as of 2019); use the
--verbose option to get the original behavior.
• File lookup with the environment variable CWEBINPUTS is extended to
permit several, colon-separated, paths; see ENVIRONMENT below.
• If properly configured, the main programs ctangle and cweave are lo-
calized with the “GNU gettext utilities”.
OPTIONS
Options on the command line may be either turned off with `-' (if they
are on by default) or turned on with `+' (if they are off by default).
In fact, the options are processed from left to right, so a sequence
like --verbose -h will only show the banner line (+b) and the progress
report (+p), but leave out the happy message (-h).
The first batch of options are common to both ctangle and cweave:
• +b: print banner line on terminal
• +h: print success message on completion
• +p: print progress report messages
• +q/-q: shortcut for -bhp; also --quiet (default)
• +v/-v: shortcut for +bhp; also --verbose
• +c: check temporary output for changes
• +s: print usage statistics
• --help: display help message and exit
• --version: output version information and exit
There are two other options applicable to ctangle only:
• +k: keep separators in numeric literals in the output
• +u: transliterate UTF-8 characters in C code
There are eight other options applicable to cweave only:
• -e: do not enclose C/C++ material in \PB{...}
• -f: do not force a newline after every C/C++ statement in output
• -F: do not force a compound statement to start on a new line
• -i: suppress indentation of parameter declarations
• -o: suppress separation of declarations and statements
• -x: omit indices, section names, table of contents
• +lX/-lX: use macros for language X as of Xcwebmac.tex
• +t: treat typename in a template like typedef
ENVIRONMENT
The environment variable CWEBINPUTS is used to search for the input
files, or the system default if CWEBINPUTS is not set. See tex(1) for
the details of the searching. To avoid conflicts with other programs
that also use the CWEBINPUTS environment, you can be more specific and
use CWEBINPUTS_cweb for special requirements in CWEB.
If prepared for NLS support, ctangle and cweave use the environment
variable TEXMFLOCALEDIR to configure the parent directory where the “GNU
gettext utilities” search for translation catalogs.
These variables are preconfigured in TeX Live’s texmf.cnf.
FILES
The location of the files mentioned below varies from system to system.
Use the kpsewhich utility to find their locations.
• cwebmac.tex: The default TeX macros \input in the first line of the
cweave output file.
• cwebman.tex: The CWEB user manual, available in PDF from ]8;;https://ctan.org/pkg/cweb\CTAN]8;;\.
SEE ALSO
• The CWEB System of Structured Documentation: by Donald E. Knuth and
Silvio Levy (hardcopy version of cwebman.tex and the source code list-
ings of common.w, ctangle.w, and cweave.w).
• Literate Programming: by D. E. Knuth.
• Weaving a Program: by Wayne Sewell.
cweb(1), tex(1), cc(1)
AUTHORS
Don Knuth wrote WEB for TeX and Pascal.
Silvio Levy designed and developed CWEB by adapting the WEB conventions
to C and by recoding everything in CWEB. Knuth began using CWEB and
made further refinements.
Many other helpers are acknowledged in the CWEB manual.
Contemporary development on https://github.com/ascherer/cweb.
Web2c 2025/dev March 10, 2024 CWEB(1)
Generated by dwww version 1.16 on Tue Dec 16 06:18:35 CET 2025.