cpp - The C Preprocessor


   cpp [-Dmacro[=defn]...] [-Umacro]
       [-Idir...] [-iquotedir...]
       [-M|-MM] [-MG] [-MF filename]
       [-MP] [-MQ target...]
       [-MT target...]
       [-P] [-fno-working-directory]
       [-x language] [-std=standard]
       infile outfile

   Only the most useful options are listed here; see below for the


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

   The C preprocessor is intended to be used only with C, C++, and
   Objective-C source code.  In the past, it has been abused as a general
   text processor.  It will choke on input which does not obey C's lexical
   rules.  For example, apostrophes will be interpreted as the beginning
   of character constants, and cause errors.  Also, you cannot rely on it
   preserving characteristics of the input which are not significant to
   C-family languages.  If a Makefile is preprocessed, all the hard tabs
   will be removed, and the Makefile will not work.

   Having said that, you can often get away with using cpp on things which
   are not C.  Other Algol-ish programming languages are often safe
   (Pascal, Ada, etc.) So is assembly, with caution.  -traditional-cpp
   mode preserves more white space, and is otherwise more permissive.
   Many of the problems can be avoided by writing C or C++ style comments
   instead of native language comments, and keeping macros simple.

   Wherever possible, you should use a preprocessor geared to the language
   you are writing in.  Modern versions of the GNU assembler have macro
   facilities.  Most high level programming languages have their own
   conditional compilation and inclusion mechanism.  If all else fails,
   try a true general text processor, such as GNU M4.

   C preprocessors vary in some details.  This manual discusses the GNU C
   preprocessor, which provides a small superset of the features of ISO
   Standard C.  In its default mode, the GNU C preprocessor does not do a
   few things required by the standard.  These are features which are
   rarely, if ever, used, and may cause surprising changes to the meaning
   of a program which does not expect them.  To get strict ISO Standard C,
   you should use the -std=c90, -std=c99 or -std=c11 options, depending on
   which version of the standard you want.  To get all the mandatory
   diagnostics, you must also use -pedantic.

   This manual describes the behavior of the ISO preprocessor.  To
   minimize gratuitous differences, where the ISO preprocessor's behavior
   does not conflict with traditional semantics, the traditional
   preprocessor should behave the same way.  The various differences that
   do exist are detailed in the section Traditional Mode.

   For clarity, unless noted otherwise, references to CPP in this manual
   refer to GNU CPP.


   The C preprocessor expects two file names 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 either file is omitted, it means the same as if - had been specified
   for that file.

   Unless otherwise noted, or the option ends in =, all options which take
   an argument may have that argument appear either immediately after the
   option, or with a space between option and argument: -Ifoo and -I foo
   have the same effect.

   Many options have multi-letter names; therefore multiple single-letter
   options may not be grouped: -dM is very different from -d -M.

   -D name
       Predefine name as a macro, with definition 1.

   -D name=definition
       The contents of definition are tokenized and processed as if they
       appeared during translation phase three in a #define directive.  In
       particular, the definition will be truncated by embedded newline

       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 wish to define a function-like macro on the command line,
       write its argument list with surrounding parentheses before the
       equals sign (if any).  Parentheses are meaningful to most shells,
       so you will need to quote the option.  With sh and csh,
       -D'name(args...)=definition' works.

       -D and -U options are processed in the order they are given on the
       command line.  All -imacros file and -include file options are
       processed after all -D and -U options.

   -U name
       Cancel any previous definition of name, either built in or provided
       with a -D option.

       Do not predefine any system-specific or GCC-specific macros.  The
       standard predefined macros remain defined.

   -I dir
       Add the directory dir to the list of directories to be searched for
       header files.

       Directories named by -I are searched before the standard system
       include directories.  If the directory dir is a standard system
       include directory, the option is ignored to ensure that the default
       search order for system directories and the special treatment of
       system headers are not defeated .  If dir begins with "=", then the
       "=" will be replaced by the sysroot prefix; see --sysroot and

   -o file
       Write output to file.  This is the same as specifying file as the
       second non-option argument to cpp.  gcc has a different
       interpretation of a second non-option argument, so you must use -o
       to specify the output file.

       Turns on all optional warnings which are desirable for normal code.
       At present this is -Wcomment, -Wtrigraphs, -Wmultichar and a
       warning about integer promotion causing a change of sign in "#if"
       expressions.  Note that many of the preprocessor's warnings are on
       by default and have no options to control them.

       Warn whenever a comment-start sequence /* appears in a /* comment,
       or whenever a backslash-newline appears in a // comment.  (Both
       forms have the same effect.)

       Most trigraphs in comments cannot affect the meaning of the
       program.  However, a trigraph that would form an escaped newline
       (??/ at the end of a line) can, by changing where the comment
       begins or ends.  Therefore, only trigraphs that would form escaped
       newlines produce warnings inside a comment.

       This option is implied by -Wall.  If -Wall is not given, this
       option is still enabled unless trigraphs are enabled.  To get
       trigraph conversion without warnings, but get the other -Wall
       warnings, use -trigraphs -Wall -Wno-trigraphs.

       Warn about certain constructs that behave differently in
       traditional and ISO C.  Also warn about ISO C constructs that have
       no traditional C equivalent, and problematic constructs which
       should be avoided.

       Warn whenever an identifier which is not a macro is encountered in
       an #if directive, outside of defined.  Such identifiers are
       replaced with zero.

       Warn about macros defined in the main file that are unused.  A
       macro is used if it is expanded or tested for existence at least
       once.  The preprocessor will also warn if the macro has not been
       used at the time it is redefined or undefined.

       Built-in macros, macros defined on the command line, and macros
       defined in include files are not warned about.

       Note: If a macro is actually used, but only used in skipped
       conditional blocks, then CPP will report it as unused.  To avoid
       the warning in such a case, you might improve the scope of the
       macro's definition by, for example, moving it into the first
       skipped block.  Alternatively, you could provide a dummy use with
       something like:

               #if defined the_macro_causing_the_warning

       Warn whenever an #else or an #endif are followed by text.  This
       usually happens in code of the form

               #if FOO
               #else FOO
               #endif FOO

       The second and third "FOO" should be in comments, but often are not
       in older programs.  This warning is on by default.

       Make all warnings into hard errors.  Source code which triggers
       warnings will be rejected.

       Issue warnings for code in system headers.  These are normally
       unhelpful in finding bugs in your own code, therefore suppressed.
       If you are responsible for the system library, you may want to see

   -w  Suppress all warnings, including those which GNU CPP issues by

       Issue all the mandatory diagnostics listed in the C standard.  Some
       of them are left out by default, since they trigger frequently on
       harmless code.

       Issue all the mandatory diagnostics, and make all mandatory
       diagnostics into errors.  This includes mandatory diagnostics that
       GCC issues without -pedantic but treats as warnings.

   -M  Instead of outputting the result of preprocessing, output a rule
       suitable for make describing the dependencies of the main source
       file.  The preprocessor outputs one make rule containing the object
       file name for that source file, a colon, and the names of all the
       included files, including those coming from -include or -imacros
       command-line options.

       Unless specified explicitly (with -MT or -MQ), the object file name
       consists of the name of the source file with any suffix replaced
       with object file suffix and with any leading directory parts
       removed.  If there are many included files then the rule is split
       into several lines using \-newline.  The rule has no commands.

       This option does not suppress the preprocessor's debug output, such
       as -dM.  To avoid mixing such debug output with the dependency
       rules you should explicitly specify the dependency output file with
       -MF, or use an environment variable like DEPENDENCIES_OUTPUT.
       Debug output will still be sent to the regular output stream as

       Passing -M to the driver implies -E, and suppresses warnings with
       an implicit -w.

   -MM Like -M but do not mention header files that are found in system
       header directories, nor header files that are included, directly or
       indirectly, from such a header.

       This implies that the choice of angle brackets or double quotes in
       an #include directive does not in itself determine whether that
       header will appear in -MM dependency output.  This is a slight
       change in semantics from GCC versions 3.0 and earlier.

   -MF file
       When used with -M or -MM, specifies a file to write the
       dependencies to.  If no -MF switch is given the preprocessor sends
       the rules to the same place it would have sent preprocessed output.

       When used with the driver options -MD or -MMD, -MF overrides the
       default dependency output file.

   -MG In conjunction with an option such as -M requesting dependency
       generation, -MG assumes missing header files are generated files
       and adds them to the dependency list without raising an error.  The
       dependency filename is taken directly from the "#include" directive
       without prepending any path.  -MG also suppresses preprocessed
       output, as a missing header file renders this useless.

       This feature is used in automatic updating of makefiles.

   -MP This option instructs CPP to add a phony target for each dependency
       other than the main file, causing each to depend on nothing.  These
       dummy rules work around errors make gives if you remove header
       files without updating the Makefile to match.

       This is typical output:

               test.o: test.c test.h


   -MT target
       Change the target of the rule emitted by dependency generation.  By
       default CPP takes the name of the main input file, deletes any
       directory components and any file suffix such as .c, and appends
       the platform's usual object suffix.  The result is the target.

       An -MT option will set the target to be exactly the string you
       specify.  If you want multiple targets, you can specify them as a
       single argument to -MT, or use multiple -MT options.

       For example, -MT '$(objpfx)foo.o' might give

               $(objpfx)foo.o: foo.c

   -MQ target
       Same as -MT, but it quotes any characters which are special to
       Make.  -MQ '$(objpfx)foo.o' gives

               $$(objpfx)foo.o: foo.c

       The default target is automatically quoted, as if it were given
       with -MQ.

   -MD -MD is equivalent to -M -MF file, except that -E is not implied.
       The driver determines file based on whether an -o option is given.
       If it is, the driver uses its argument but with a suffix of .d,
       otherwise it takes the name of the input file, removes any
       directory components and suffix, and applies a .d suffix.

       If -MD is used in conjunction with -E, any -o switch is understood
       to specify the dependency output file, but if used without -E, each
       -o is understood to specify a target object file.

       Since -E is not implied, -MD can be used to generate a dependency
       output file as a side-effect of the compilation process.

       Like -MD except mention only user header files, not system header

   -x c
   -x c++
   -x objective-c
   -x assembler-with-cpp
       Specify the source language: C, C++, Objective-C, or assembly.
       This has nothing to do with standards conformance or extensions; it
       merely selects which base syntax to expect.  If you give none of
       these options, cpp will deduce the language from the extension of
       the source file: .c, .cc, .m, or .S.  Some other common extensions
       for C++ and assembly are also recognized.  If cpp does not
       recognize the extension, it will treat the file as C; this is the
       most generic mode.

       Note: Previous versions of cpp accepted a -lang option which
       selected both the language and the standards conformance level.
       This option has been removed, because it conflicts with the -l

       Specify the standard to which the code should conform.  Currently
       CPP knows about C and C++ standards; others may be added in the

       standard may be one of:

           The ISO C standard from 1990.  c90 is the customary shorthand
           for this version of the standard.

           The -ansi option is equivalent to -std=c90.

           The 1990 C standard, as amended in 1994.

           The revised ISO C standard, published in December 1999.  Before
           publication, this was known as C9X.

           The revised ISO C standard, published in December 2011.  Before
           publication, this was known as C1X.

           The 1990 C standard plus GNU extensions.  This is the default.

           The 1999 C standard plus GNU extensions.

           The 2011 C standard plus GNU extensions.

           The 1998 ISO C++ standard plus amendments.

           The same as -std=c++98 plus GNU extensions.  This is the
           default for C++ code.

   -I- Split the include path.  Any directories specified with -I options
       before -I- are searched only for headers requested with
       "#include "file""; they are not searched for "#include <file>".  If
       additional directories are specified with -I options after the -I-,
       those directories are searched for all #include directives.

       In addition, -I- inhibits the use of the directory of the current
       file directory as the first search directory for "#include "file"".

       This option has been deprecated.

       Do not search the standard system directories for header files.
       Only the directories you have specified with -I options (and the
       directory of the current file, if appropriate) are searched.

       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 the C++ library.)

   -include file
       Process file as if "#include "file"" appeared as the first line of
       the primary source file.  However, the first directory searched for
       file is the preprocessor's working directory instead of the
       directory containing the main source file.  If not found there, it
       is searched for in the remainder of the "#include "..."" search
       chain as normal.

       If multiple -include options are given, the files are included in
       the order they appear on the command line.

   -imacros file
       Exactly like -include, except that any output produced by scanning
       file is thrown away.  Macros it defines remain defined.  This
       allows you to acquire all the macros from a header without also
       processing its declarations.

       All files specified by -imacros are processed before all files
       specified by -include.

   -idirafter dir
       Search dir for header files, but do it after all directories
       specified with -I and the standard system directories have been
       exhausted.  dir is treated as a system include directory.  If dir
       begins with "=", then the "=" will be replaced by the sysroot
       prefix; see --sysroot and -isysroot.

   -iprefix prefix
       Specify prefix as the prefix for subsequent -iwithprefix options.
       If the prefix represents a directory, you should include the final

   -iwithprefix dir
   -iwithprefixbefore dir
       Append dir to the prefix specified previously with -iprefix, and
       add the resulting directory to the include search path.
       -iwithprefixbefore puts it in the same place -I would; -iwithprefix
       puts it where -idirafter would.

   -isysroot dir
       This option is like the --sysroot option, but applies only to
       header files (except for Darwin targets, where it applies to both
       header files and libraries).  See the --sysroot option for more

   -imultilib dir
       Use dir as a subdirectory of the directory containing target-
       specific C++ headers.

   -isystem dir
       Search dir for header files, after all directories specified by -I
       but before the standard system directories.  Mark it as a system
       directory, so that it gets the same special treatment as is applied
       to the standard system directories.

       If dir begins with "=", then the "=" will be replaced by the
       sysroot prefix; see --sysroot and -isysroot.

   -iquote dir
       Search dir only for header files requested with "#include "file"";
       they are not searched for "#include <file>", before all directories
       specified by -I and before the standard system directories.

       If dir begins with "=", then the "=" will be replaced by the
       sysroot prefix; see --sysroot and -isysroot.

       When preprocessing, handle directives, but do not expand macros.

       The option's behavior depends on the -E and -fpreprocessed options.

       With -E, preprocessing is limited to the handling of directives
       such as "#define", "#ifdef", and "#error".  Other preprocessor
       operations, such as macro expansion and trigraph conversion are not
       performed.  In addition, the -dD option is implicitly enabled.

       With -fpreprocessed, predefinition of command line and most builtin
       macros is disabled.  Macros such as "__LINE__", which are
       contextually dependent, are handled normally.  This enables
       compilation of files previously preprocessed with "-E

       With both -E and -fpreprocessed, the rules for -fpreprocessed take
       precedence.  This enables full preprocessing of files previously
       preprocessed with "-E -fdirectives-only".

       Accept $ in identifiers.

       Accept universal character names in identifiers.  This option is
       enabled by default for C99 (and later C standard versions) and C++.

       When preprocessing, do not shorten system header paths with

       Indicate to the preprocessor that the input file has already been
       preprocessed.  This suppresses things like macro expansion,
       trigraph conversion, escaped newline splicing, and processing of
       most directives.  The preprocessor still recognizes and removes
       comments, so that you can pass a file preprocessed with -C to the
       compiler without problems.  In this mode the integrated
       preprocessor is little more than a tokenizer for the front ends.

       -fpreprocessed is implicit if the input file has one of the
       extensions .i, .ii or .mi.  These are the extensions that GCC uses
       for preprocessed files created by -save-temps.

       Set the distance between tab stops.  This helps the preprocessor
       report correct column numbers in warnings or errors, even if tabs
       appear on the line.  If the value is less than 1 or greater than
       100, the option is ignored.  The default is 8.

       This option is only useful for debugging GCC.  When used with -E,
       dumps debugging information about location maps.  Every token in
       the output is preceded by the dump of the map its location belongs
       to.  The dump of the map holding the location of a token would be:


       When used without -E, this option has no effect.

       Track locations of tokens across macro expansions. This allows the
       compiler to emit diagnostic about the current macro expansion stack
       when a compilation error occurs in a macro expansion. Using this
       option makes the preprocessor and the compiler consume more memory.
       The level parameter can be used to choose the level of precision of
       token location tracking thus decreasing the memory consumption if
       necessary. Value 0 of level de-activates this option just as if no
       -ftrack-macro-expansion was present on the command line. Value 1
       tracks tokens locations in a degraded mode for the sake of minimal
       memory overhead. In this mode all tokens resulting from the
       expansion of an argument of a function-like macro have the same
       location. Value 2 tracks tokens locations completely. This value is
       the most memory hungry.  When this option is given no argument, the
       default parameter value is 2.

       Note that "-ftrack-macro-expansion=2" is activated by default.

       Set the execution character set, used for string and character
       constants.  The default is UTF-8.  charset can be any encoding
       supported by the system's "iconv" library routine.

       Set the wide execution character set, used for wide string and
       character constants.  The default is UTF-32 or UTF-16, whichever
       corresponds to the width of "wchar_t".  As with -fexec-charset,
       charset can be any encoding supported by the system's "iconv"
       library routine; however, you will have problems with encodings
       that do not fit exactly in "wchar_t".

       Set the input character set, used for translation from the
       character set of the input file to the source character set used by
       GCC.  If the locale does not specify, or GCC cannot get this
       information from the locale, the default is UTF-8.  This can be
       overridden by either the locale or this command-line option.
       Currently the command-line option takes precedence if there's a
       conflict.  charset can be any encoding supported by the system's
       "iconv" library routine.

       Enable generation of linemarkers in the preprocessor output that
       will let the compiler know the current working directory at the
       time of preprocessing.  When this option is enabled, the
       preprocessor will emit, after the initial linemarker, a second
       linemarker with the current working directory followed by two
       slashes.  GCC will use this directory, when it's present in the
       preprocessed input, as the directory emitted as the current working
       directory in some debugging information formats.  This option is
       implicitly enabled if debugging information is enabled, but this
       can be inhibited with the negated form -fno-working-directory.  If
       the -P flag is present in the command line, this option has no
       effect, since no "#line" directives are emitted whatsoever.

       Do not print column numbers in diagnostics.  This may be necessary
       if diagnostics are being scanned by a program that does not
       understand the column numbers, such as dejagnu.

   -A predicate=answer
       Make an assertion with the predicate predicate and answer answer.
       This form is preferred to the older form -A predicate(answer),
       which is still supported, because it does not use shell special

   -A -predicate=answer
       Cancel an assertion with the predicate predicate and answer answer.

       CHARS is a sequence of one or more of the following characters, and
       must not be preceded by a space.  Other characters are interpreted
       by the compiler proper, or reserved for future versions of GCC, and
       so are silently ignored.  If you specify characters whose behavior
       conflicts, the result is undefined.

       M   Instead of the normal output, generate a list of #define
           directives for all the macros defined during the execution of
           the preprocessor, including predefined macros.  This gives you
           a way of finding out what is predefined in your version of the
           preprocessor.  Assuming you have no file foo.h, the command

                   touch foo.h; cpp -dM foo.h

           will show all the predefined macros.

           If you use -dM without the -E option, -dM is interpreted as a
           synonym for -fdump-rtl-mach.

       D   Like M except in two respects: it does not include the
           predefined macros, and it outputs both the #define directives
           and the result of preprocessing.  Both kinds of output go to
           the standard output file.

       N   Like D, but emit only the macro names, not their expansions.

       I   Output #include directives in addition to the result of

       U   Like D except that only macros that are expanded, or whose
           definedness is tested in preprocessor directives, are output;
           the output is delayed until the use or test of the macro; and
           #undef directives are also output for macros tested but
           undefined at the time.

   -P  Inhibit generation of linemarkers 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 linemarkers.

   -C  Do not discard comments.  All comments are passed through to the
       output file, except for comments in processed directives, which are
       deleted along with the directive.

       You should be prepared for side effects when using -C; it causes
       the preprocessor to treat comments as tokens in their own right.
       For example, comments appearing at the start of what would be a
       directive line have the effect of turning that line into an
       ordinary source line, since the first token on the line is no
       longer a #.

   -CC Do not discard comments, including during macro expansion.  This is
       like -C, except that comments contained within macros are also
       passed through to the output file where the macro is expanded.

       In addition to the side-effects of the -C option, the -CC option
       causes all C++-style comments inside a macro to be converted to
       C-style comments.  This is to prevent later use of that macro from
       inadvertently commenting out the remainder of the source line.

       The -CC option is generally used to support lint comments.

       Try to imitate the behavior of old-fashioned C preprocessors, as
       opposed to ISO C preprocessors.

       Process trigraph sequences.

       Enable special code to work around file systems which only permit
       very short file names, such as MS-DOS.

       Print text describing all the command-line options instead of
       preprocessing anything.

   -v  Verbose mode.  Print out GNU CPP's version number at the beginning
       of execution, and report the final form of the include path.

   -H  Print the name of each header file used, in addition to other
       normal activities.  Each name is indented to show how deep in the
       #include stack it is.  Precompiled header files are also printed,
       even if they are found to be invalid; an invalid precompiled header
       file is printed with ...x and a valid one with ...! .

       Print out GNU CPP's version number.  With one dash, proceed to
       preprocess as normal.  With two dashes, exit immediately.


   This section describes the environment variables that affect how CPP
   operates.  You can use them to specify directories or prefixes to use
   when searching for include files, or to control dependency output.

   Note that you can also specify places to search using options such as
   -I, and control dependency output with options like -M.  These take
   precedence over environment variables, which in turn take precedence
   over the configuration of GCC.

       Each variable's value is a list of directories separated by a
       special character, much like PATH, in which to look for header
       files.  The special character, "PATH_SEPARATOR", is target-
       dependent and determined at GCC build time.  For Microsoft Windows-
       based targets it is a semicolon, and for almost all other targets
       it is a colon.

       CPATH specifies a list of directories to be searched as if
       specified with -I, but after any paths given with -I options on the
       command line.  This environment variable is used regardless of
       which language is being preprocessed.

       The remaining environment variables apply only when preprocessing
       the particular language indicated.  Each specifies a list of
       directories to be searched as if specified with -isystem, but after
       any paths given with -isystem options on the command line.

       In all these variables, an empty element instructs the compiler to
       search its current working directory.  Empty elements can appear at
       the beginning or end of a path.  For instance, if the value of
       CPATH is ":/special/include", that has the same effect as
       -I. -I/special/include.

       If this variable is set, its value specifies how to output
       dependencies for Make based on the non-system header files
       processed by the compiler.  System header files are ignored in the
       dependency output.

       The value of DEPENDENCIES_OUTPUT can be just a file name, in which
       case the Make rules are written to that file, guessing the target
       name from the source file name.  Or the value can have the form
       file target, in which case the rules are written to file file using
       target as the target name.

       In other words, this environment variable is equivalent to
       combining the options -MM and -MF, with an optional -MT switch too.

       This variable is the same as DEPENDENCIES_OUTPUT (see above),
       except that system header files are not ignored, so it implies -M
       rather than -MM.  However, the dependence on the main input file is

       If this variable is set, its value specifies a UNIX timestamp to be
       used in replacement of the current date and time in the "__DATE__"
       and "__TIME__" macros, so that the embedded timestamps become

       The value of SOURCE_DATE_EPOCH must be a UNIX timestamp, defined as
       the number of seconds (excluding leap seconds) since 01 Jan 1970
       00:00:00 represented in ASCII; identical to the output of
       @command{date +%s} on GNU/Linux and other systems that support the
       %s extension in the "date" command.

       The value should be a known timestamp such as the last modification
       time of the source or package and it should be set by the build


   gpl(7), gfdl(7), fsf-funding(7), gcc(1), as(1), ld(1), and the Info
   entries for cpp, gcc, and binutils.


   Copyright (c) 1987-2016 Free Software Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document
   under the terms of the GNU Free Documentation License, Version 1.3 or
   any later version published by the Free Software Foundation.  A copy of
   the license is included in the man page gfdl(7).  This manual contains
   no Invariant Sections.  The Front-Cover Texts are (a) (see below), and
   the Back-Cover Texts are (b) (see below).

   (a) The FSF's Front-Cover Text is:

        A GNU Manual

   (b) The FSF's Back-Cover Text is:

        You have freedom to copy and modify this GNU Manual, like GNU
        software.  Copies published by the Free Software Foundation raise
        funds for GNU development.


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.