Gengetopt is a tool to write command line option parsing code for C programs.
This is Edition 2.22.5 of the Gengetopt manual.
This file documents GNU Gengetopt version 2.22.5.
This manual is for GNU Gengetopt (version 2.22.5, 25 September 2011), a tool to write command line option parsers for C programs.
Copyright © 2001 - 2011 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 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being “A GNU Manual,” and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License.”(a) 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.”
Gengetopt is a tool to generate C code to parse the command line
arguments argc and argv that are part of every C or C++
program. The generated code uses the C library function
getopt_long to perform the actual command line parsing.
This manual is written for C and C++ programmers, specifically the lazy ones. If you've written any non-trivial C program, you've had to deal with argument parsing. It isn't particularly difficult, nor is it particularly exciting. It is one of the classic programming nuisances, which is why most books on programming leave it as an exercise for the reader. Gengetopt can save you from this work, leaving you free to focus on the interesting parts of your program.
Thus your program will be able to handle command line options such as:
myprog --input foo.c -o foo.o --no-tabs -i 100 *.class
And both long options (those that start with --) and short
options (start with - and consist of only one character) can be
handled (see Terminology for further details). For standards about
short and long options you may want to take a look at the GNU Coding
Standards (http://www.gnu.org/prep/standards_toc.html).
Gengetopt can also generate a function to save the command line options into a file (see Basic Usage), and a function to read the command line options from a file (see Configuration files). Of course, these two kinds of files are compliant.
Generated code works also if you use GNU Autoconf and GNU Automake and
it is documented with Doxygen comments. In particular,
PACKAGE,
PACKAGE_NAME and
VERSION are used in the generated code
to print information.
Gengetopt is free software; you are free to use, share and modify it under the terms of the GNU General Public License that accompanies this manual.
The code that Gengetopt generates is also free software; however it is licensed with a simple all-permissive license instead of the GPL or LGPL. You are free to do anything you like with the generated code, including incorporating it into or linking it with proprietary software.
Gengetopt was originally written by Roberto Arturo Tena Sanchez. It is currently maintained by Lorenzo Bettini http://www.lorenzobettini.it.
A primordial version of Terminology was written by Adam Greenblatt.
See the file INSTALL for detailed building and installation instructions; anyway if you're used to compiling Linux software that comes with sources you may simply follow the usual procedure, i.e. untar the file you downloaded in a directory and then:
cd <source code main directory>
./configure
make
make install
Note: unless you specify a different install directory by
--prefix option of
configure (e.g. ./configure --prefix=<your home>),
you must be root to run make install.
Files will be installed in the following directories:
executables/prefix/bin
docs/prefix/share/doc/gengetopt
examples/prefix/share/doc/gengetopt/examples
additional files/prefix/share/gengetopt
Default value for prefix is /usr/local
but you may change it with --prefix
option to configure.
You can download it from GNU's ftp site: ftp://ftp.gnu.org/gnu/gengetopt or from one of its mirrors (see http://www.gnu.org/prep/ftp.html).
I do not distribute Windows binaries anymore; since, they can be easily built by using Cygnus C/C++ compiler, available at http://www.cygwin.com. However, if you don't feel like downloading such compiler, you can request such binaries directly to me, by e-mail (find my e-mail at my home page) and I can send them to you.
Archives are digitally signed by me (Lorenzo Bettini) with GNU gpg (http://www.gnupg.org). My GPG public key can be found at my home page (http://www.lorenzobettini.it).
You can also get the patches, if they are available for a particular release (see below for patching from a previous version).
This project's git repository can be checked out through the following clone instruction1:
git clone git://git.savannah.gnu.org/gengetopt.git
Further instructions can be found at the address:
http://savannah.gnu.org/projects/gengetopt.
And the git repository can also browsed on-line at
http://git.savannah.gnu.org/cgit/gengetopt.git.
Please note that this way you will get the latest development sources of Gengetopt, which may also be unstable. This solution is the best if you intend to correct/extend this program: you should send me patches against the latest git repository sources.
If, on the contrary, you want to get the sources of a given release,
through git, say, e.g., version X.Y.Z, you must specify the tag
rel_X_Y_Z.
When you compile the sources that you get from the git repository,
before running the configure and make commands, for the
first time, you must run the command:
autoreconf -i
This will run the autotools commands in the correct order, and also copy
possibly missing files. You should have installed recent versions of
automake, autoconf and libtool in order for this to
succeed.
Gengetopt has been developed under GNU/Linux, using gcc (C++), and bison (yacc) and flex (lex), and ported under Win32 with Cygnus C/C++compiler, available at http://www.cygwin.com.
For developing gengetopt, I use the excellent
GNU Autoconf2,
GNU Automake3 and
GNU Libtool4.
Since version 2.19 I also started to use Gnulib - The GNU Portability
Library5, “a central
location for common GNU code, intended to be shared among GNU packages”
(for instance, I rely on Gnulib for checking for the presence and
correctness of getopt_long function, Use Gnulib).
Moreover GNU Gengen (http://www.gnu.org/software/gengen) is used for automatically generating the code that generates the command line parser.
Actually, you don't need all these tools above to build gengetopt because I provide generated sources, unless you want to develop gengetopt.
The code generated by gengetopt relies on the getopt_long
function that is usually in the standard C library; however, there may
be some implementations of the C library that don't include it; we refer
to No getopt_long, for instructions on how to check whether
getopt_long is part of the library and how to deal with their lacking
(using autoconf and automake).
If you downloaded a patch, say gengetopt-1.3-1.3.1-patch.gz (i.e., the patch to go from version 1.3 to version 1.3.1), cd to the directory with sources from the previous version (gengetopt-1.3) and type:
gunzip -cd ../gengetopt-1.3-1.3.1.patch.gz | patch -p1
and restart the compilation process (if you had already run configure a simple make should do).
The command line options, which have to be handled by gengetopt
generated function, are specified in a file (typically with .ggo
extension). This file consists of sentences with the formats shown below
(these sentences are allowed to span more than one line). Statements in
{} are optional (the option sentences need not to be given in
separate lines):
package "<packname>"
version "<version>"
purpose "<purpose>"
usage "<usage>"
description "<description>"
args "<command line options>"
option <long> <short> "<desc>"
{details="<detailed description>"}
{argtype} {typestr="<type descr>"}
{values="<value1>","<value2>",...}
{default="<default value>"}
{dependon="<other option>"}
{required} {argoptional} {multiple}
{hidden}
option <long> <short> "<desc>" flag <on/off>
section "section name" {sectiondesc="optional section description"}
text "a textual sentence"
Where:
packagePACKAGE and
PACKAGE_NAME generated by autoconf.
This is required, unless you use autoconf.
If package is specified, then it will be used to print the
program name in the output of --help and --version, and
also when printing errors (from within the generated parser). If it is
not specified, then PACKAGE will be used when printing errors,
and PACKAGE_NAME in the output of --help and
--version. Note that if PACKAGE_NAME is empty, then
PACKAGE will be used also in this case.
versionVERSION generated by autoconf.
This is required, unless you use autoconf.
purposeusagedescriptionargsargs8 you can specify options
that will be added to the command line options of gengetopt itself. For
instance, if you always run gengetopt on your input file with the
options --no-handle-error --string-parser -u, you can add these
options in the input file like this:
args "--no-handle-error --string-parser -u"
and remove those recurrent options from the command line.
Optional.
long-) and a dot (.). No spaces
allowed. The name of the variables generated to store arguments (see
later in this section) are long options converted to be legal C variable
names. This means that . and - are both replaced by
_.
short- is specified, then no short option is considered for the long
option (thus long options with no associated short options are allowed).
Since version 2.22 you can also specify ? as the short option.
desc--help. Wrapping will be automatically performed.
details--detailed-help9, which will be
automatically generated. Thus, these further details will NOT be
printed with --help. Wrapping will be automatically performed.
Optional.
argtypestring, int, short, long, float,
double, longdouble or longlong. If the option is
an enumerated one (see Options with enumerated values) the type
can also be enum. If no type is specified the option does not
accept an argument.
typestr--help (e.g., "filename" instead
of simply STRING, or "portnumber" instead of simply
INT).
valuesenum. More on this feature
can be found in Options with enumerated values.
defaultmultiple flag (Multiple Options) but only by
giving a single default value. It is not possible to specify a list of
default values.
dependonrequiredrequired or optional. This specifies whether such option
must be given at each program invocation. These keywords were
introduced in release 2.17. Before, you had to use the keywords
yes or no. You can still use these keywords but their use
is not advised since they are not much explicative.
If not specified, an option is considered mandatory; if you do not want
this behavior, you can require that by default options are considered
optional, by using the command line option
--default-optional11.
argoptional= in case you use a long option, and avoid spaces if
you use short option. For instance, if the option with optional
argument is -B|--bar, use the following command line syntax:
-B15 or --bar=15, and NOT the following one -B 15
nor --bar 15.
By using this specification together with default you can obtain
an option that even if not explicitly specified will have the default
value, and if it is specified without an argument it will have, again,
the default value.
multiplerequired flag. See Multiple Options.
hidden--help but it can still be specified at command
line12. In case hidden options are used,
the command line option --full-help will also be generated. This
will print also the hidden options13. If
there's an option with details, then also
--detailed-help14 will be
automatically generated; if one then specifies --detailed-help
also hidden options will be printed (besides the details for options).
on/offon or off. This is the state of the flag when the program
starts. If user specifies the option, the flag toggles.
For strings (delimited by ") the following convention is
adopted15: a string
spanning more than one line will be interpreted with the corresponding
line breaks; if the line break is not desired one can use the backslash
\ to break the line without inserting a line break. A line break
in a string can also be inserted with the string \n. Here are
some examples:
"This string will be interpreted
into two lines exactly as it is"
"This string is specified with two lines \
but interpreted as specified in only one line \
i.e., without explicit line break"
"This string\nwill have a line break"
Moreover, if the character " must be specified in the string, it
will have to be escaped with the backslash16:
"This string contains \"a quoted string\" inside"
The part that must be provided in the correct order is
option <long> <short> "<desc>"
while the other specifications can be given in any order17. Thus, for instance
option <long> <short> "<desc>" {argtype} {typestr="<type descr>"}
is the same as
option <long> <short> "<desc>" {typestr="<type descr>"} {argtype}
Comments begin with # in any place (but in strings) of the line
and ends in the end of line.
Notice that the options -h,--help and
-V,--version are added automatically; however, if you specify an
option yourself that has h as short form, then only --help
is added18. The same holds for
-V,--version.
In case hidden options are used, See Hidden options, the
command line option --full-help will also be generated. This
will print also the hidden options19.
If there's at least one option with details, the command line
option --detailed-help will also be generated. This will print
also the details for options and hidden options20.
Options can be part of sections, that provide a more meaningful
descriptions of the options. A section can be defined with the
following syntax (the sectiondesc is optional) and all the options
following a section declaration are considered part of that sections:
section "section name" {sectiondesc="optional section description"}
Notice that the separation in sections is stronger than separation in
groups of mutual exclusive options (see Group options).
Furthermore, sections should not be inserted among group options (but
only externally). A section makes sense only if it is followed by some
options. If you don't specify any option after a section, that section
will not be printed at all. If you need to simply insert some text in
the output of --help, then you must use text, explained in
the next paragraph.
You can insert, among options, a textual string that will be printed in
the output of --help21:
text "\nA text description with possible line\nbreaks"
Of course, you can use this mechanism even to manually insert blank lines among options with an empty text string:
text ""
You can also specify the list of values that can be passed to an
option (if the type is not specified, the option has type
string). More on this feature can be found in Options with enumerated values. If a value that is not in the list is passed, an
error is raised. You can think of such options as enumerated
options. It is not necessary to pass the complete value at the command
line option: a non ambiguous prefix will do. For instance, if the
accepted values are "foo","bar","foobar", then you can pass at
the command line the value "b" and the value "bar" will be
selected, or the value "foob" and the value "foobar" will
be selected; instead, passing the value "fo" will raise an
ambiguity error.
Here's an example of such a file (the file is called sample1.ggo)
# Name of your program
package "sample1" # don't use package if you're using automake
# Version of your program
version "2.0" # don't use version if you're using automake
# Options
option "str-opt" s "A string option, for a filename"
string typestr="filename" optional
text "\nA brief text description"
text " before the other options.\n"
option "my-opt" m "Another integer option, \
this time the description of the option should be \"quite\" long to \
require wrapping... possibly more than one wrapping :-) \
especially if I\nrequire a line break" int optional
option "int-opt" i "A int option" int yes
section "more involved options"
sectiondesc="the following options\nare more complex"
text ""
option "flag-opt" - "A flag option" flag off
option "funct-opt" F "A function option" optional
details="\nA function option is basically an option with no argument.\
It can be used, e.g., to specify a specific behavior for a program.
Well, this further explanation is quite useless, but it's only to \
show an example of an option with details, \
which will be printed only when --detailed-help is given \
at the command line."
section "last option section"
option "long-opt" - "A long option" long optional
option "def-opt" - "A string option with default"
string default="Hello" optional
option "enum-opt" - "A string option with list of values"
values="foo","bar","hello","bye" default="hello" optional
option "secret" S "hidden option will not appear in --help"
int optional hidden
option "dependant" D
"option that depends on str-opt" int optional dependon="str-opt"
text "\nAn ending text."
The simplest way to use gengetopt is to pass this file as the standard input, i.e.:
gengetopt < sample1.ggo
By default gengetopt generates cmdline.h and cmdline.c. Otherwise we can specify these names with a command line option:
gengetopt < sample1.ggo --file-name=cmdline1 --unamed-opts
The option --unamed-opts allows the generated command line parser
to accept also names, without an option (for instance you can pass a
file name without an option in front of it, and also use wildcards, such
as *.c, foo*.? and so on). These are also called
parameters (see Terminology). You can specify an optional
description for these additional names (default is FILES).
In cmdline1.h you'll find the generated C struct:
/** @file cmdline1.h
* @brief The header file for the command line option parser
* generated by GNU Gengetopt version 2.22.5
* http://www.gnu.org/software/gengetopt.
* DO NOT modify this file, since it can be overwritten
* @author GNU Gengetopt by Lorenzo Bettini */
#ifndef CMDLINE1_H
#define CMDLINE1_H
/* If we use autoconf. */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdio.h> /* for FILE */
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
#ifndef CMDLINE_PARSER_PACKAGE
/** @brief the program name (used for printing errors) */
#define CMDLINE_PARSER_PACKAGE "sample1"
#endif
#ifndef CMDLINE_PARSER_PACKAGE_NAME
/** @brief the complete program name (used for help and version) */
#define CMDLINE_PARSER_PACKAGE_NAME "sample1"
#endif
#ifndef CMDLINE_PARSER_VERSION
/** @brief the program version */
#define CMDLINE_PARSER_VERSION "2.0"
#endif
/** @brief Where the command line options are stored */
struct gengetopt_args_info
{
const char *help_help; /**< @brief Print help and exit help description. */
const char *detailed_help_help; /**< @brief Print help, including all details and hidden options, and exit help description. */
const char *full_help_help; /**< @brief Print help, including hidden options, and exit help description. */
const char *version_help; /**< @brief Print version and exit help description. */
char * str_opt_arg; /**< @brief A string option, for a filename. */
char * str_opt_orig; /**< @brief A string option, for a filename original value given at command line. */
const char *str_opt_help; /**< @brief A string option, for a filename help description. */
int my_opt_arg; /**< @brief Another integer option, this time the description of the option should be \"quite\" long to require wrapping... possibly more than one wrapping :-) especially if I
require a line break. */
char * my_opt_orig; /**< @brief Another integer option, this time the description of the option should be \"quite\" long to require wrapping... possibly more than one wrapping :-) especially if I
require a line break original value given at command line. */
const char *my_opt_help; /**< @brief Another integer option, this time the description of the option should be \"quite\" long to require wrapping... possibly more than one wrapping :-) especially if I
require a line break help description. */
int int_opt_arg; /**< @brief A int option. */
char * int_opt_orig; /**< @brief A int option original value given at command line. */
const char *int_opt_help; /**< @brief A int option help description. */
int flag_opt_flag; /**< @brief A flag option (default=off). */
const char *flag_opt_help; /**< @brief A flag option help description. */
const char *funct_opt_help; /**< @brief A function option help description. */
long long_opt_arg; /**< @brief A long option. */
char * long_opt_orig; /**< @brief A long option original value given at command line. */
const char *long_opt_help; /**< @brief A long option help description. */
char * def_opt_arg; /**< @brief A string option with default (default='Hello'). */
char * def_opt_orig; /**< @brief A string option with default original value given at command line. */
const char *def_opt_help; /**< @brief A string option with default help description. */
char * enum_opt_arg; /**< @brief A string option with list of values (default='hello'). */
char * enum_opt_orig; /**< @brief A string option with list of values original value given at command line. */
const char *enum_opt_help; /**< @brief A string option with list of values help description. */
int secret_arg; /**< @brief hidden option will not appear in --help. */
char * secret_orig; /**< @brief hidden option will not appear in --help original value given at command line. */
const char *secret_help; /**< @brief hidden option will not appear in --help help description. */
int dependant_arg; /**< @brief option that depends on str-opt. */
char * dependant_orig; /**< @brief option that depends on str-opt original value given at command line. */
const char *dependant_help; /**< @brief option that depends on str-opt help description. */
unsigned int help_given ; /**< @brief Whether help was given. */
unsigned int detailed_help_given ; /**< @brief Whether detailed-help was given. */
unsigned int full_help_given ; /**< @brief Whether full-help was given. */
unsigned int version_given ; /**< @brief Whether version was given. */
unsigned int str_opt_given ; /**< @brief Whether str-opt was given. */
unsigned int my_opt_given ; /**< @brief Whether my-opt was given. */
unsigned int int_opt_given ; /**< @brief Whether int-opt was given. */
unsigned int flag_opt_given ; /**< @brief Whether flag-opt was given. */
unsigned int funct_opt_given ; /**< @brief Whether funct-opt was given. */
unsigned int long_opt_given ; /**< @brief Whether long-opt was given. */
unsigned int def_opt_given ; /**< @brief Whether def-opt was given. */
unsigned int enum_opt_given ; /**< @brief Whether enum-opt was given. */
unsigned int secret_given ; /**< @brief Whether secret was given. */
unsigned int dependant_given ; /**< @brief Whether dependant was given. */
char **inputs ; /**< @brief unamed options (options without names) */
unsigned inputs_num ; /**< @brief unamed options number */
} ;
/** @brief The additional parameters to pass to parser functions */
struct cmdline_parser_params
{
int override; /**< @brief whether to override possibly already present options (default 0) */
int initialize; /**< @brief whether to initialize the option structure gengetopt_args_info (default 1) */
int check_required; /**< @brief whether to check that all required options were provided (default 1) */
int check_ambiguity; /**< @brief whether to check for options already specified in the option structure gengetopt_args_info (default 0) */
int print_errors; /**< @brief whether getopt_long should print an error message for a bad option (default 1) */
} ;
/** @brief the purpose string of the program */
extern const char *gengetopt_args_info_purpose;
/** @brief the usage string of the program */
extern const char *gengetopt_args_info_usage;
/** @brief all the lines making the help output */
extern const char *gengetopt_args_info_help[];
/** @brief all the lines making the full help output (including hidden options) */
extern const char *gengetopt_args_info_full_help[];
/** @brief all the lines making the detailed help output (including hidden options and details) */
extern const char *gengetopt_args_info_detailed_help[];
/**
* The command line parser
* @param argc the number of command line options
* @param argv the command line options
* @param args_info the structure where option information will be stored
* @return 0 if everything went fine, NON 0 if an error took place
*/
int cmdline_parser (int argc, char **argv,
struct gengetopt_args_info *args_info);
/**
* The command line parser (version with additional parameters - deprecated)
* @param argc the number of command line options
* @param argv the command line options
* @param args_info the structure where option information will be stored
* @param override whether to override possibly already present options
* @param initialize whether to initialize the option structure my_args_info
* @param check_required whether to check that all required options were provided
* @return 0 if everything went fine, NON 0 if an error took place
* @deprecated use cmdline_parser_ext() instead
*/
int cmdline_parser2 (int argc, char **argv,
struct gengetopt_args_info *args_info,
int override, int initialize, int check_required);
/**
* The command line parser (version with additional parameters)
* @param argc the number of command line options
* @param argv the command line options
* @param args_info the structure where option information will be stored
* @param params additional parameters for the parser
* @return 0 if everything went fine, NON 0 if an error took place
*/
int cmdline_parser_ext (int argc, char **argv,
struct gengetopt_args_info *args_info,
struct cmdline_parser_params *params);
/**
* Save the contents of the option struct into an already open FILE stream.
* @param outfile the stream where to dump options
* @param args_info the option struct to dump
* @return 0 if everything went fine, NON 0 if an error took place
*/
int cmdline_parser_dump(FILE *outfile,
struct gengetopt_args_info *args_info);
/**
* Save the contents of the option struct into a (text) file.
* This file can be read by the config file parser (if generated by gengetopt)
* @param filename the file where to save
* @param args_info the option struct to save
* @return 0 if everything went fine, NON 0 if an error took place
*/
int cmdline_parser_file_save(const char *filename,
struct gengetopt_args_info *args_info);
/**
* Print the help
*/
void cmdline_parser_print_help(void);
/**
* Print the full help (including hidden options)
*/
void cmdline_parser_print_full_help(void);
/**
* Print the detailed help (including hidden options and details)
*/
void cmdline_parser_print_detailed_help(void);
/**
* Print the version
*/
void cmdline_parser_print_version(void);
/**
* Initializes all the fields a cmdline_parser_params structure
* to their default values
* @param params the structure to initialize
*/
void cmdline_parser_params_init(struct cmdline_parser_params *params);
/**
* Allocates dynamically a cmdline_parser_params structure and initializes
* all its fields to their default values
* @return the created and initialized cmdline_parser_params structure
*/
struct cmdline_parser_params *cmdline_parser_params_create(void);
/**
* Initializes the passed gengetopt_args_info structure's fields
* (also set default values for options that have a default)
* @param args_info the structure to initialize
*/
void cmdline_parser_init (struct gengetopt_args_info *args_info);
/**
* Deallocates the string fields of the gengetopt_args_info structure
* (but does not deallocate the structure itself)
* @param args_info the structure to deallocate
*/
void cmdline_parser_free (struct gengetopt_args_info *args_info);
/**
* Checks that all the required options were specified
* @param args_info the structure to check
* @param prog_name the name of the program that will be used to print
* possible errors
* @return
*/
int cmdline_parser_required (struct gengetopt_args_info *args_info,
const char *prog_name);
extern const char *cmdline_parser_enum_opt_values[]; /**< @brief Possible values for enum-opt. */
#ifdef __cplusplus
}
#endif /* __cplusplus */
#endif /* CMDLINE1_H */
First of all, notice that the argv parameter (typically
corresponding to the homonimous argument of your program's main
function) is declared as char ** and not as char *const
*22. Actually,
the version of getopt_long in libc uses prototypes with
char *const *argv that are incorrect because getopt_long and
getopt_long_only can permute argv; this is required for backward
compatibility (e.g., for LSB 2.0.1)23. So, it is better to declare
argv as char ** in the generated parser functions.
The <option>_given field is set to 1 when an argument for
<option> has been specified (otherwise it is 0)24. This fields also
counts the times a multiple option is specified (see Multiple Options). If the option accepts an argument and it is not of
flag type The <option>_arg field is set to the value
passed at the command line. The <option>_arg field has the
corresponding C type specified in the file passed to gengetopt.
Notice that if an option has a default value, then the corresponding
<option>_arg will be initialized with that value but the
corresponding <option>_given will NOT be initialized to 1. Thus,
<option>_given will effectively inform you if the user has
specified that command line option.
The additional field <option>_orig is always a string containing
the original value passed at the command line. This may be different,
for instance, in case of numerical arguments: gengetopt converts the
passed value (a string) into the corresponding numerical type; due to
conversions, float representations, etc., this may not correspond
exactly to the original value passed at command line. It can also be
different when enumerated options are used (see above): in particular
the <option>_arg field will contain a value taken from the
specified list, while <option>_orig contains the (non-ambiguous)
prefix specified at the command line.
The user can always access this original value by using
<option>_orig instead of <option>_arg, as he sees
fit25. For instance, gengetopt itself uses the original value when it
saves the command line options into a file (see the _file_save
function in the following). However, apart from very specific command
line processing, the user might hardly need the <option>_orig
field, and can be always safely use <option>_arg.
The <option>_help contains the string (concerning this very
option) that is printed when --help command line is given.
If it is of flag type, only the field <option>_flag
is generated.
The strings cmdline_parser_purpose and
cmdline_parser_usage contain the purpose as specified in
the input file and the generated “usage” string as printed when
--help command line is given. Finally, the string array
cmdline_parser_help contains the strings (one for each option)
printed when --help command line is given (this array is
terminated by a null string element). If hidden options are used also
the cmdline_parser_full_help array is available (containing also
help strings concerning hidden options). If at least one option has
details, then the cmdline_parser_detailed_help array is
available (containing also help strings concerning hidden options and
details for options). All these strings can be used by the programmer
to build a customized help output26.
Even if <option>_given is 0, the corresponding
<option>_arg is set to default value (if one has been specified
for <option>). However, in this case, the <option>_orig
is set to NULL.
Notice that by default the generated function is called
cmdline_parser (see the command line options below, to override
this name), and it takes the arguments that main receives and a
pointer to such a struct, that it will be filled. Another version,
cmdline_parser2, can be specified more arguments. Since you
typically need this second version only in conjunction with other
“kinds” of parsers such as configuration files and multiple parsers,
you can find more details about it in