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)
texlive-bin 2026.78235 - Generated Thu Mar 5 16:06:03 CST 2026