DOKK / manpages / debian 10 / preprocess / preprocess.1.en
PREPROCESS(1) General Commands Manual PREPROCESS(1)

preprocess - Preprocess a file.

preprocess [options...] infile

Preprocess is like a typical C preprocessor, but it extends to multiple languages. Languages for which it works include: C++, Python, Perl, Tcl, XML, JavaScript, CSS, IDL, TeX, Fortran, PHP, Java, Shell scripts (Bash, CSH, etc.) and C#. Preprocess is usable both as a command line app and as a Python module.

Print help text and exit.
Print the version info and exit.
Give verbose output for errors.
Write output to the given file instead of to stdout.
Overwrite given output file. Otherwise an IOError will be raised if outfile already exists.
Define a variable for preprocessing. define can simply be a variable name (in which case it will be true) or it can be of the form var=val. An attempt will be made to convert val to an integer so "-D FOO=0" will create a false value.
Add a directory to the include path for #include directives.
Emit empty lines for preprocessor statement lines and skipped output lines. This allows line numbers to stay constant.
Substitute defines into emitted lines. By default substitution is NOT done because it currently will substitute into program strings.


from preprocess import preprocess
preprocess(infile, outfile=sys.stdout, defines={}, force=0,
keepLines=0, includePath=[], substitute=0)

The <infile> can be marked up with special preprocessor statement lines of the form:


<comment-prefix> <preprocessor-statement> <comment-suffix>

where the <comment-prefix/suffix> are the native comment delimiters for that file type.

HTML (*.htm, *.html) or XML (*.xml, *.kpf, *.xul) files:


<!-- #if FOO -->
...
<!-- #endif -->

Python (*.py), Perl (*.pl), Tcl (*.tcl), Ruby (*.rb), Bash (*.sh), or make ([Mm]akefile*) files:


# #if defined('FAV_COLOR') and FAV_COLOR == "blue"
...
# #elif FAV_COLOR == "red"
...
# #else
...
# #endif

C (*.c, *.h), C++ (*.cpp, *.cxx, *.cc, *.h, *.hpp, *.hxx, *.hh), Java (*.java), PHP (*.php) or C# (*.cs) files:


// #define FAV_COLOR 'blue'
...
/* #ifndef FAV_COLOR */
...
// #endif

Fortran 77 (*.f) or 90/95 (*.f90) files:


C #if COEFF == 'var'
...
C #endif

Valid statements:


#define <var> [<value>]
#undef <var>
#ifdef <var>
#ifndef <var>
#if <expr>
#elif <expr>
#else
#endif
#error <error string>
#include "<file>"

where <expr> is any valid Python expression.

The expression after #if/elif may be a Python statement. It is an error to refer to a variable that has not been defined by a -D option or by an in-content #define.

Special built-in methods for expressions:


defined(varName) Return true if given variable is defined.

A suggested file naming convention is to let input files to preprocess be of the form <basename>.p.<ext> and direct the output of preprocess to <basename>.<ext>, e.g.:


preprocess -o foo.py foo.p.py

The advantage is that other tools (esp. editors) will still recognize the unpreprocessed file as the original language.

Trent Mick <trentm@gmail.com>

This manual page was written by Johannes Ring <johannr@simula.no> for the Debian GNU/Linux system (but may be used by others).