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(libc.info)Argp

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Parsing Program Options with Argp
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   "Argp" is an interface for parsing unix-style argument vectors.
Note: Program Arguments.

   Argp provides features unavailable in the more commonly used
`getopt' interface.  These features include automatically producing
output in response to the `--help' and `--version' options, as
described in the GNU coding standards.  Using argp makes it less likely
that programmers will neglect to implement these additional options or
keep them up to date.

   Argp also provides the ability to merge several independently defined
option parsers into one, mediating conflicts between them and making the
result appear seamless.  A library can export an argp option parser that
user programs might employ in conjunction with their own option parsers,
resulting in less work for the user programs.  Some programs may use
only argument parsers exported by libraries, thereby achieving
consistent and efficient option-parsing for abstractions implemented by
the libraries.

   The header file `<argp.h>' should be included to use argp.

The `argp_parse' Function
-------------------------

   The main interface to argp is the `argp_parse' function.  In many
cases, calling `argp_parse' is the only argument-parsing code needed in
`main'.  Note: Program Arguments.

 - Function: error_t argp_parse (const struct argp *ARGP, int ARGC,
          char **ARGV, unsigned FLAGS, int *ARG_INDEX, void *INPUT)
     The `argp_parse' function parses the arguments in ARGV, of length
     ARGC, using the argp parser ARGP.  Note: Argp Parsers.

     A value of zero is the same as a `struct argp'containing all
     zeros.  FLAGS is a set of flag bits that modify the parsing
     behavior.  Note: Argp Flags.  INPUT is passed through to the argp
     parser ARGP, and has meaning defined by ARGP.  A typical usage is
     to pass a pointer to a structure which is used for specifying
     parameters to the parser and passing back the results.

     Unless the `ARGP_NO_EXIT' or `ARGP_NO_HELP' flags are included in
     FLAGS, calling `argp_parse' may result in the program exiting.
     This behavior is true if an error is detected, or when an unknown
     option is encountered.  Note: Program Termination.

     If ARG_INDEX is non-null, the index of the first unparsed option
     in ARGV is returned as a value.

     The return value is zero for successful parsing, or an error code
     (Note: Error Codes) if an error is detected.  Different argp
     parsers may return arbitrary error codes, but the standard error
     codes are: `ENOMEM' if a memory allocation error occurred, or
     `EINVAL' if an unknown option or option argument is encountered.

Globals

Argp Global Variables. Global argp parameters.

Parsers

Argp Parsers. Defining parsers for use with `argp_parse'.

Flags

Argp Flags. Flags that modify the behavior of `argp_parse'.

Help

Argp Help. Printing help messages when not parsing.

Examples

Argp Examples. Simple examples of programs using argp.

Customization

Argp User Customization.

Users may control the `--help' output format.