extract file[.sgml]
Extracts the source code out of a literate program written using
the qwertz SGML document type. The syntax of the document is
checked while the source code is being extracted. If syntax errors
are found, error messages are written to standard error and the
program may terminate before all code has been extracted. The code
being extracted is written to standard out, but this will usually be
redirected to a file with some appropriate file name extension,
depending on the programming language being used. The ".sgml" filename
extension of the input file is optional.
For example, if the input file is named foo.sgml and
contains the source code of a C program, you could extract and compile
the program by typing:
extract foo > foo.c cc foo
In this example, as standard error has not been redirected, error messages will appear on the terminal.
SGML syntax errors are written to standard error. If the input file
contains such errors, extract will terminate with exit status 1
before all the code has been extracted from the file.