Linux Complete Command Reference:User Commands:EarthWeb Inc.-

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_V, —version-control	The type of backups made can be set with the VERSION_CONTROL environment variable, which
{numbered,existing,simple}	can be overridden by this option. If VERSION_CONTROL is not set and this option is not given, the default backup type is existing. The value of the VERSION_CONTROL environment variable and the argument to this option are like the GNU emacs version- control variable; they also recognize synonyms that are more descriptive. The valid values are (unique abbreviations are accepted) the following:

	t or numbered	Always make numbered backups
	nil or existing	Make numbered backups of files that already have them, simple backups of the others
	never or simple	Always make simple backups

cccp, cpp

cccp, cpp—The GNU C-compatible compiler preprocessor

SYNOPSIS


cccp    [_$][_A predicate [( value )]] [ _C ][_D name [ = definition ]]

        [_dD][_dM][_I\ directory ][_H ][_I_ ][_imacros file ][_

        include file ][_idirafter dir ][_iprefix prefix ][_iwithprefix dir ]

        [ _lang_c][_lang_c++][_lang_objc ][_lang_objc++ ][_lint ][_

        M[_MG ]] [ _MM[_MG ]] [ _MD file ][_MMD file ][_nostdinc ]

        [ _nostdinc++][_P][_pedantic ][_pedantic_errors ][_traditional ]

        [ _trigraphs ][_U name ][_undef ][_Wtrigraphs ][_Wcomment ]

        [ _Wall ][_Wtraditional ]

        [ infile |_ ][ outfile |_ ]

DESCRIPTION

The C preprocessor is a macro processor that is used automatically by the C compiler to transform your program before actual compilation. It is called a macro processor because it allows you to define macros, which are brief abbreviations for longer constructs.

The C preprocessor provides four separate facilities that you can use as you see fit:

Inclusion of header files. These are files of declarations that can be substituted into your program.
Macro expansion. You can define macros, which are abbreviations for arbitrary fragments of C code, and then the C preprocessor will replace the macros with their definitions throughout the program.
Conditional compilation. Using special preprocessing directives, you can include or exclude parts of the program according to various conditions.
Line control. If you use a program to combine or rearrange source files into an intermediate file which is then compiled, you can use line control to inform the compiler of where each source line originally came from.

C preprocessors vary in some details. For a full explanation of the GNU C preprocessor, see the info file cpp.info, or the manual The C Preprocessor . Both of these are built from the same documentation source file, cpp.texinfo. The GNU C preprocessor provides a superset of the features of ANSI Standard C.

ANSI Standard C requires the rejection of many harmless constructs commonly used by today's C programs. Such incompatibility would be inconvenient for users, so the GNU C preprocessor is configured to accept these constructs by default. Strictly speaking, to get ANSI Standard C, you must use the options _trigraphs, _undef, and _pedantic, but in practice the consequences of having strict ANSI Standard C make it undesirable to do this.

When you use the C preprocessor, you will usually not have to invoke it explicitly: the C compiler will do so automatically. However, the preprocessor is sometimes useful individually.

When you call the preprocessor individually, either name (cpp or cccp) will do; they are completely synonymous.

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The C preprocessor expects two filenames as arguments, infile and outfile. The preprocessor reads infile together with any other files it specifies with #include. All the output generated by the combined input files is written in outfile. Either infile or outfile may be _, which as infile means to read from standard input and as outfile means to write to standard output. Also, if outfile or both filenames are omitted, the standard output and standard input are used for the omitted filenames.

OPTIONS

Here is a table of command options accepted by the C preprocessor. These options can also be given when compiling a C program; they are passed along automatically to the preprocessor when it is invoked by the compiler.

_P	Inhibit generation of # lines with line-number information in the output from the preprocessor. This might be useful when running the preprocessor on something that is not C code and will be sent to a program which might be confused by the # lines.
_C	Do not discard comments: pass them through to the output file. Comments appearing in arguments of a macro call will be copied to the output before the expansion of the macro call.
_traditional	Try to imitate the behavior of old-fashioned C, as opposed to ANSI C.
_trigraphs	Process ANSI standard trigraph sequences. These are three-character sequences, all starting with ??, that are defined by ANSI C to stand for single characters. For example, ??/ stands for \, so ??/n is a character constant for a newline. Strictly speaking, the GNU C preprocessor does not support all programs in ANSI Standard C unless _trigraphs is used, but if you ever notice the difference, it will be with relief. You don't want to know any more about trigraphs.
_pedantic	Issue warnings required by the ANSI C standard in certain cases such as when text other than a comment follows #else or #endif.
_pedantic_errors	Like _pedantic, except that errors are produced rather than warnings.
_Wtrigraphs	Warn if any trigraphs are encountered (assuming they are enabled).
_Wcomment	Warn whenever a comment-start sequence /* appears in a comment. (Both forms have the
_Wcomments	same effect.)
_Wall	Requests both _Wtrigraphs and _Wcomment (but not _Wtraditional).
_Wtraditional	Warn about certain constructs that behave differently in traditional and ANSI C.
_I directory	Add the directory directory to the end of the list of directories to be searched for header files. This can be used to override a system header file, substituting your own version, since these directories are searched before the system header file directories. If you use more than one _I option, the directories are scanned in left-to-right order; the standard system directories come after.
_I_	Any directories specified with _I options before the _I_ option are searched only for the case of #include " file "; they are not searched for #include < file >.
	If additional directories are specified with _I options after the _I_, these directories are searched for all #include directives.
	In addition, the _I_ option inhibits the use of the current directory as the first search directory for #include " file ". Therefore, the current directory is searched only if it is requested explicitly with _I followed by a period (.). Specifying both _I_ and _I. allows you to control precisely which directories are searched before the current one and which are searched after.
_nostdinc	Do not search the standard system directories for header files. Only the directories you have specified with _I options (and the current directory, if appropriate) are searched.
_nostdinc++	Do not search for header files in the C++-specific standard directories, but do still search the other standard directories. (This option is used when building libg++.)
_D name	Predefine name as a macro, with definition 1.
_D name=definition	Predefine name as a macro, with definition definition. There are no restrictions on the contents of definition, but if you are invoking the preprocessor from a shell or shell-like program, you may need to use the shell's quoting syntax to protect characters such as spaces that have a meaning in the shell syntax. If you use more than one _D for the same name, the rightmost definition takes effect.

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