cpp – C language preprocessor


cpp [ option ... ] [ ifile [ ofile ] ]


Cpp interprets ANSI C preprocessor directives and does macro substitution. The input ifile and output ofile default to standard input and standard output respectively.

The options are:






Same as in 2c(1): add dir to the search for  

unhandled troff command .CW



Generate no output except a list of include files in a form suitable for specifying dependencies to mk(1). Use twice to list files in angle brackets.  


Turn off default include directories. All must be specified with -I, or in the environment variable include. Without this option, /$objtype/include and /sys/include are used as the last two searched directories for include directives, where $objtype is read from the environment.  


Print extra debugging information.  


Do not insert #line directives into the output.  


Understand C++ comments.  


Inhibit include search in the source’s directory.  


Print the list of directories searched when #include is found. Last listed are searched first.  

In the absence of the -P option, the processed text output is sprinkled with lines that show the original input line numbering:

#line linenumber "ifile"  

The command reads the environment variable include and adds its (blank-separated) list of directories to the standard search path for

unhandled troff command .CW

directives. They are looked at before any directories specified with -I, which are looked at before the default directories.

The input language is as described in the ANSI C standard. The standard Plan 9 C compilers do not use cpp; they contain their own simple but adequate preprocessor, so cpp is usually superfluous.



directory for machine-independent include files  


directory for machine-dependent include files