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Man Pages

Manual Reference Pages  -  CTANGLE (1)


ctangle, cweave - translate CWEB to C and/or TeX




ctangle [-bhp] [+s] webfile[.w] [{changefile[.ch]|-} [outfile[.c]]]
cweave [-befhpx] [+s] webfile[.w] [{changefile[.ch]|-} [outfile[.tex]]]


The ctangle program converts a CWEB source document into a 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, italics, boldface, etc., and it supplies extensive cross-index information that it gathers automatically.

CWEB allows you to prepare a single document containing all the information that is needed both to produce a compilable C program and to produce a well-formatted document describing the program in as much detail as the writer may desire. The user of CWEB ought to be familiar with TeX as well as C.

The command line should have one, two, or three names on it. The first is taken as the CWEB file (and .w is added if there is no extension). If that file cannot be opened, the extension .web is tried instead. (But .w is recommended, since .web usually implies Pascal.) 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 WEB 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 .c or .tex.

Options in 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 -f +f corresponds to +f (which is the default).

The -b option suppresses the banner line that normally appears on your terminal when ctangle or cweave begins. The -h option suppresses the happy message that normally appears if the processing was successful. The -p option suppresses progress reports (starred module numbers) as the processing takes place. If you say -bhp, you get nothing but error messages.

The +s option prints statistics about memory usage at the end of a run (assuming that the programs have been compiled with the -DSTAT switch).

There are three other options applicable to cweave only: -f means do not force a newline after every statement in the formatted output. -e inhibits the enclosure of C material formatted by cweave in brackets \PB{...}. Such brackets are normally inserted so that special hooks can be used by cweb-latex and similar programs. -x means omit the index and table of contents.


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.


The location of the files mentioned below varies from system to system. Use the kpsewhich utility to find their locations.
  TeX macros used by cweave output.
  The user manual.


Literate Programming
  by D. E. Knuth.
Weaving a Program
  by Wayne Sewell.
The CWEB System of Structured Documentation
  by Donald E. Knuth and Silvio Levy (hardcopy version of cwebman.tex and the source code listings).
tex(1), cc(1).


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.

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Web2C 2015 CWEB (1) 7 April 2010

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