TANGLE(1)                   General Commands Manual                  TANGLE(1)

NAME
       tangle, otangle - translate a literate programming WEB to Pascal

SYNOPSIS
       tangle [options] webfile[.web] [{changefile[.ch]|-} [outfile[.p]]]

DESCRIPTION
       The tangle program converts a WEB literate programming source document
       into a Pascal program. In addition to being processed with a Pascal
       compiler, nowadays, the Pascal output is often translated to C; this is
       how the TeX family of programs are compiled in TeX Live.

       The WEB language allows you to prepare a single document containing all
       the information that is needed to produce both a compilable Pascal
       program and a well-formatted document describing the program in as much
       detail as the writer may desire. The user of WEB must be familiar with
       both TeX and Pascal. WEB also provides a relatively simple, although
       adequate, macro facility that permits a Pascal program to be written in
       small modules, written in an arbitrary order.

       The command line should have one, two or three filenames on it. The
       first is taken as the WEB file; ".web" is added if there is no
       extension.

       If a second filename is given, it is taken as 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 WEB system documentation. If no
       second filename, there is no change file.

       If a third filename is given, it is taken as the Pascal output file,
       and ".p" is added if there is no extension. To specify an output file
       with no change, you can use "-" for the second argument, meaning an
       empty change file (not stdin). If no third filename is given, the name
       of the Pascal file is formed by adding ".p" to the root of the WEB file
       name.

       The output file is packed into lines of 72 characters or less, with the
       only concession to readability being the termination of lines at
       semicolons when this can be done conveniently.

       If the WEB program uses the built-in string handling feature (double-
       quoted strings), a second output file is a string pool file, whose name
       is always formed by adding ".pool" to the root of the Pascal file name.

       The otangle variant supports a larger character range. It was written
       for the Omega project, the first TeX supporting Unicode, now provided
       as the aleph(1) descendant program.

OPTIONS
       See tex(1) for details of command-line parsing.

       Some of these options may render the output unsuitable for processing
       by a Pascal compiler.

       --help Print help message and exit.

       --length number
              Compare only the first number characters of identifiers when
              checking for collisions.  The default is 32; the original tangle
              used 7.

       --loose
              When checking for collisions between identifiers, honor the
              settings of the --lowercase, --mixedcase, --uppercase, and
              --underline options. This is the default.

       --lowercase
              Convert all identifiers to lowercase.

       --mixedcase
              Retain the case of identifiers.  This is the default.

       --strict
              When checking for collisions between identifiers, strip
              underlines and convert all identifiers to uppercase first.

       --underline
              Retain underlines (also known as underscores) in identifiers.

       --uppercase
              Convert all identifiers to uppercase.  This is the behaviour of
              the original tangle.

       --version
              Print version information and exit.

       otangle supports only the --help and --version options,

ENVIRONMENT
       The programs look for the input files using the environment variable
       WEBINPUTS. If it is not set, it uses the system default. See the
       Kpathsea manual at https://tug.org/kpathsea for the details of the
       searching.

SEE ALSO
       Donald E. Knuth, The WEB System of Structured Documentation.
       https://mirrors.ctan.org/info/knuth-pdf/web/webman.pdf

       Donald E. Knuth, LiterateProgramming, CSLI Lecture Notes, no. 27.
       https://www-cs-faculty.stanford.edu/~knuth/lp.html

       Donald E. Knuth, TeX: The Program (Volume B of Computers &
       Typesetting).
       Donald E. Knuth, Metafont: The Program (Volume D of Computers &
       Typesetting).
       These latter two are by far the largest extant examples of WEB
       programs.

       Literate programming topic on CTAN: https://ctan.org/topic/litprog
       Package page on CTAN: https://ctan.org/pkg/tangle
       Section in the Web2c manual:
       https://tug.org/texinfohtml/web2c.html#tangle-invocation
       Typeset source code for all the original Stanford WEB programs:
       https://ctan.org/pkg/knuth-pdf

AUTHORS
       WEB was designed by Donald E. Knuth, based on an earlier system called
       DOC (implemented by Ignacio Zabala), inspired by considerable earlier
       work, notably Pierre-Arnoul de Marneffe's concept of ``holon
       programming'' (https://github.com/holon-scribe/holon-programming).

       The updates for Omega were written by John Plaice and Yannis
       Haralambous.

       The tangle and weave programs are themselves written in WEB. The system
       was originally ported to Unix at Stanford by Howard Trickey, and at
       Cornell by Pavel Curtis.

       Public discussion list and bug reports: https://lists.tug.org/tex-k

Web2C 2026                      25 January 2026                      TANGLE(1)