GNU Gengetopt 2.14


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Gengetopt

Gengetopt is a tool to write option parsing code for C programs.

This is Edition 2.14 of the Gengetopt manual.

It documents GNU Gengetopt version 2.14.


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Audience

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.


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Gengetopt Copying Conditions

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.


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1 Installation

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.

1.1 Download

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).

1.2 Anonymous CVS Access

This project's CVS repository can be checked out through anonymous (pserver) CVS with the following instruction set. When prompted for a password for anoncvs, simply press the Enter key.

     cvs -d:pserver:anoncvs@subversions.gnu.org:/cvsroot/gengetopt login
     
     cvs -z3 -d:pserver:anoncvs@subversions.gnu.org:/cvsroot/gengetopt \
       co gengetopt

Further instructions can be found at the address:

http://savannah.gnu.org/projects/gengetopt.

Please notice 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 cvs repository sources.

If, on the contrary, you want to get the sources of a given release, through cvs, say, e.g., version X.Y.Z, you must specify the tag rel_X_Y_Z when you run the cvs command or the cvs update command.

When you compile the sources that you get through the cvs repository, before running the configure and make commands, you should, at least the first time, run the command:

     sh reconf

This will run the autotools commands in the correct order, and also copy possibly missing files. You should have installed recent versions of automake and autoconf in order for this to succeed. You will also need flex and bison.

NOTICE: This convention holds since release 2.14.

1.3 What you need to build gengetopt

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. I used the excellent GNU Autoconf and GNU Automake. I also used Autotools (ftp://ftp.ugcs.caltech.edu/pub/elef/autotools) which creates a starting source tree (according to GNU standards) with autoconf, automake starting files.

Moreover Gengen (http://www.lorenzobettini.it/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 source-highlight because I provide generated sources, unless you want to develop source-highlight.

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; in this case you have to link the program that uses the file generated by gengetopt with the files getopt.c and getopt1.c and include gnugetopt.h in your project. We obviously provide these files in the utility files directory (<install prefix>/share/gengetopt). These files are part of the GNU C library. You may want to take a look at getopt_long man page.

Read also 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).

1.4 Patching from a previous version

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).


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2 Basic Usage

The command line options, which have to be handled by gengetopt generated function, are specified in a file (typically with .ggo extension). This file consist in lines of sentences with the following formats, commands in {} are optional1:

     package <packname>
     version <version>
     
     option <long> <short> <desc> {argtype} {typestr="<type descr>"} \
         {default="<default value>"} {required} {argoptional} {multiple}
     option <long> <short> <desc> {typestr="<type descr>"} \
         {values="value1","value2",...} {default="<default value>"} \
         {required} {argoptional} {multiple}
     option <long> <short> <desc> flag <on/off>

Where:

package
Double quoted string. This has the precedence over PACKAGE generated by autoconf.
version
Double quoted string. This has the precedence over VERSION generated by autoconf.
purpose
What the program does (even on more than one line), it will be printed with the help. Double quoted string.
long
The long option, a double quoted string with upper and lower case characters, digits, a dash (-) 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
The short option, a single upper or lower case char, or a digit. If a - is specified, then no short option is considered for the long option (thus long options with no associated short options are allowed).
desc
Double quoted string with upper and lower case characters, digits, a dash (-) and a dot (.). The first character must not be a space. This description will be printed during the output of --help. Wrapping will be automatically performed, and \n is interpreted as a newline request.
argtype
string, int, short, long, float, double, longdouble or longlong. If no type is specified the option does not accept an argument.
typestr
a description for the type of the values for the option. This will be used during the output of --help (e.g., "filename" instead of simply STRING, or "portnumber" instead of simply INT).
values
a list of strings containing all the possible values that can be passed to the option. The type is considered string and must not be specified.
default
an optional default value for the option. The value must always be specified as a double quoted string.
required
yes or no. This specifies whether such option must be given at each program invocation.
argoptional
If this flag is specified then this option has an argument that is optional. In this case, when you specify the argument at command line, please use = 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.
multiple
If this flag is specified then this option can be specified more than once at command line; all the values for this option are stored in an array. See Multiple Options.
on/off
on or off. This is the state of the flag when the program starts. If user specifies the option, the flag toggles.

Comments begins with # in any place 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 or help as long form, then -h,--help is not added (and you have to handle the help option manually). The same holds for -V,--version.

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"}

You can also specify the list of values that can be passed to an option (in that case the option has type string). If a value that is not in the list is passed, an error is raised. You can think of such options as enumerated options.

Here's an example of such a file (the file is called sample1.ggo)

     # file sample1.ggo
     option  "str-opt"     s "A string option, for a filename" \
          string typestr="filename" no
     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 no
     option  "int-opt"     i "A int option"         int        yes
     section "more involved options" \
          sectiondesc="the following options\nare more complex"
     option  "flag-opt"    - "A flag option"        flag       off
     option  "funct-opt"   F "A function option"    no
     section "last option section"
     option  "long-opt"    - "A long option"        long       no
     option  "def-opt"     - "A string option with default" \
          string default="Hello" no
     option  "enum-opt"    - "A string option with list of values" \
          values="foo","bar","hello" default="hello" no

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:

     /* cmdline1.h */
     
     /* File autogenerated by gengetopt version 2.14rc  */
     
     #ifndef CMDLINE1_H
     #define CMDLINE1_H
     
     /* If we use autoconf.  */
     #ifdef HAVE_CONFIG_H
     #include "config.h"
     #endif
     
     #ifdef __cplusplus
     extern "C" {
     #endif /* __cplusplus */
     
     #ifndef CMDLINE_PARSER_PACKAGE
     #define CMDLINE_PARSER_PACKAGE "sample1"
     #endif
     
     #ifndef CMDLINE_PARSER_VERSION
     #define CMDLINE_PARSER_VERSION "2.0"
     #endif
     
     struct gengetopt_args_info
     {
       char * str_opt_arg;       /* A string option, for a filename.  */
       char * str_opt_orig;       /* A string option, for a filename original value given at command line.  */
       int my_opt_arg;       /* 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.  */
       char * my_opt_orig;       /* 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 original value given at command line.  */
       int int_opt_arg;       /* A int option.  */
       char * int_opt_orig;       /* A int option original value given at command line.  */
       int flag_opt_flag;       /* A flag option (default=off).  */
       long long_opt_arg;       /* A long option.  */
       char * long_opt_orig;       /* A long option original value given at command line.  */
       char * def_opt_arg;       /* A string option with default (default='Hello').  */
       char * def_opt_orig;       /* A string option with default original value given at command line.  */
       char * enum_opt_arg;       /* A string option with list of values (default='hello').  */
       char * enum_opt_orig;       /* A string option with list of values original value given at command line.  */
     
       int help_given ;       /* Whether help was given.  */
       int version_given ;       /* Whether version was given.  */
       int str_opt_given ;       /* Whether str-opt was given.  */
       int my_opt_given ;       /* Whether my-opt was given.  */
       int int_opt_given ;       /* Whether int-opt was given.  */
       int flag_opt_given ;       /* Whether flag-opt was given.  */
       int funct_opt_given ;       /* Whether funct-opt was given.  */
       int long_opt_given ;       /* Whether long-opt was given.  */
       int def_opt_given ;       /* Whether def-opt was given.  */
       int enum_opt_given ;       /* Whether enum-opt was given.  */
     
       char **inputs ; /* unamed options */
       unsigned inputs_num ; /* unamed options number */
     } ;
     
     int cmdline_parser (int argc, char * const *argv, struct gengetopt_args_info *args_info);
     int cmdline_parser2 (int argc, char * const *argv, struct gengetopt_args_info *args_info, int override, int initialize, int check_required);
     int cmdline_parser_file_save(const char *filename, struct gengetopt_args_info *args_info);
     
     void cmdline_parser_print_help(void);
     void cmdline_parser_print_version(void);
     
     void cmdline_parser_init (struct gengetopt_args_info *args_info);
     void cmdline_parser_free (struct gengetopt_args_info *args_info);
     
     int cmdline_parser_required (struct gengetopt_args_info *args_info, const char *prog_name);
     
     extern char *cmdline_parser_enum_opt_values[] ;       /* Possible values for enum-opt.  */
     
     
     #ifdef __cplusplus
     }
     #endif /* __cplusplus */
     #endif /* CMDLINE1_H */
     

The <option>_given field is set to a value different from 0 when an argument for <option> has been specified. 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. 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 convertions, float representations, etc., this may not correspond exactly to the original value passed at command line. The user can always access this original value by using <option>_orig instead of <option>_arg, as he sees fit2. For instance, gengetopt itselfs uses the original value when it saves the command line options into a file (see the _file_save function in the following).

If it is of flag type, only the field <option>_flag is generated.

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.

cmdline_parser_free can be called to deallocate memory allocated by the parser for string and multiple options.

Notice that after calling this function, the parsing functions should not be called anymore.

cmdline_parser_init can be called to initialize the struct (it is not mandatory, since it is done automatically by the command line parser).

cmdline_parser_file_save3 can be used to save the command line options into a file. The contents of this file are consistent with the configuration files (Configuration files). Notice that if an option has a default value, this option will be saved into the file only if it was passed explicitly at command line (or read from a configuration file), i.e., default values will not be saved into the file.

And here's how these functions can be used inside the main program:

     /* main1.cc */
     /* we try to use gengetopt generated file in a C++ program */
     /* we don't use autoconf and automake vars */
     
     #include <iostream>
     #include "stdlib.h"
     
     #include "cmdline1.h"
     
     using std::cout;
     using std::endl;
     
     int
     main (int argc, char **argv)
     {
       gengetopt_args_info args_info;
     
       cout << "This one is from a C++ program" << endl ;
       cout << "Try to launch me with some options" << endl ;
       cout << "(type sample1 --help for the complete list)" << endl ;
       cout << "For example: ./sample1 *.* --funct-opt" << endl ;
     
       /* let's call our cmdline parser */
       if (cmdline_parser (argc, argv, &args_info) != 0)
         exit(1) ;
     
       cout << "Here are the options you passed..." << endl;
     
       for ( unsigned i = 0 ; i < args_info.inputs_num ; ++i )
         cout << "file: " << args_info.inputs[i] << endl ;
     
       if ( args_info.funct_opt_given )
         cout << "You chose --funct-opt or -F." << endl ;
     
       if ( args_info.str_opt_given )
         cout << "You inserted " << args_info.str_opt_arg << " for " <<
           "--str-opt option." << endl ;
     
       if ( args_info.int_opt_given )
         cout << "This is the integer you input: " <<
           args_info.int_opt_arg << "." << endl;
     
       if (args_info.flag_opt_given)
         cout << "The flag option was given!" << endl;
     
       cout << "The flag is " << ( args_info.flag_opt_flag ? "on" : "off" ) <<
         "." << endl ;
     
       cout << args_info.def_opt_arg << "! ";
     
       cout << "Have a nice day! :-)" << endl ;
     
       cmdline_parser_free (&args_info); /* release allocated memory */
     
       return 0;
     }
     

Now you can compile main1.cc and the cmdline1.c generated by gengetopt and link all together to obtain sample1 executable:

     gcc -c cmdline1.c
     g++ -c main1.cc
     g++ -o sample1 cmdline1.o main1.o

(Here we assume that getopt_long is included in the standard C library; see Installation and No getopt_long).

Now let's try some tests with this program:

     $ ./sample1 -s "hello" --int-opt 1234
     This one is from a C++ program
     Try to launch me with some options
     (type sample1 --help for the complete list)
     For example: ./sample1 *.* --funct-opt
     Here are the options you passed...
     You inserted hello for --str-opt option.
     This is the integer you input: 1234.
     The flag is off.
     Have a nice day! :-)

You can also pass many file names to the command line (this also shows how flags work):

     $ ./sample1 *.h -i -100 -x
     This one is from a C++ program
     Try to launch me with some options
     (type sample1 --help for the complete list)
     For example: ./sample1 *.* --funct-opt
     Here are the options you passed...
     file: cmdline1.h
     file: cmdline2.h
     file: cmdline.h
     file: getopt.h
     This is the integer you input: -100.
     The flag is on.
     Have a nice day! :-)

And if we try to omit the --int-opt (or -i), which is required, we get an error:

     $ ./sample1
     This one is from a C++ program
     Try to launch me with some options
     (type sample1 --help for the complete list)
     For example: ./sample1 *.* --funct-opt
     sample1: `--int-opt' (`-i') option required!

Here is the output of --help:

     sample1 2.0
     
     Usage: sample1 -iINT|--int-opt=INT [-h|--help] [-V|--version]
              -sfilename|--str-opt=filename -mINT|--my-opt=INT [--flag-opt]
              [-F|--funct-opt] --long-opt=LONG --def-opt=STRING  [FILES]...
     
       -h, --help              Print help and exit
       -V, --version           Print version and exit
       -s, --str-opt=filename  A string option, for a filename
       -m, --my-opt=INT        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
       -i, --int-opt=INT       A int option
     
     more involved options:
     the following options
     are more complex
           --flag-opt          A flag option  (default=off)
       -F, --funct-opt         A function option
     
     last option section:
           --long-opt=LONG     A long option
           --def-opt=STRING    A string option with default  (default=`Hello')
           --enum-opt=STRING   A string option with list of values  (possible
                                 values="foo", "bar", "hello" default=`hello')

Notice how filename is printed instead of STRING for the option --str-opt (since typestr was used in the sample1.ggo file) and how the description of --my-opt is wrapped to 80 columns, and how the \n is actually interpreted as a newline request.

If you're curious you may want to take a look at the generated C file cmdline1.c.

You may find other examples in /prefix/share/doc/gengetopt/examples or in the tests of the source tarbal.


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3 Invoking gengetopt

This is the output of gengetopt --help:

     gengetopt
     
     This program generates a C function that uses getopt_long function
     to parse the command line options, validate them and fill a struct.
     
     Usage: gengetopt [OPTIONS]...
     
       -h, --help                  Print help and exit
       -V, --version               Print version and exit
       -i, --input=filename        input file (default std input)
       -f, --func-name=name        name of generated function
                                     (default=`cmdline_parser')
       -a, --arg-struct-name=name  name of generated args info struct
                                     (default=`gengetopt_args_info')
       -F, --file-name=name        name of generated file  (default=`cmdline')
       -c, --c-extension=ext       extension of c file  (default=`c')
       -H, --header-extension=ext  extension of header file  (default=`h')
       -l, --long-help             long usage line in help
       -u, --unamed-opts[=STRING]  accept options without names (e.g., file names)
                                     (default=`FILES')
       -n, --no-handle-help        do not handle --help|-h automatically
       -N, --no-handle-version     do not handle --version|-V automatically
       -e, --no-handle-error       do not exit on errors
       -g, --gen-version           put gengetopt version in the generated file
                                     (default=on)
       -C, --conf-parser           generate a config file parser
           --set-package=STRING    set the package name (override package defined in
                                     the .ggo file)
           --set-version=STRING    set the version number (override version defined
                                     in the .ggo file)
           --show-help             show the output of --help instead of generating
                                     code
           --show-version          show the output of --version instead of
                                     generating code

The options should be clear; in particular:

--func-name
if no --func-name is given, cmdline_parser is taken by default;
--arg-struct-name
allows to specify the name of the generated struct for command line arguments (default is gengetopt_args_info)
--long-help
the “Usage” line reports all the options; this may be unpleasant if options are many;
--unamed-opts
the program will accept also options without a name, which, in most case, means that we can pass many file names to the program (see the example in Basic Usage, where we call sample1 *.h). You can specify an optional description for these additional names (default is FILES).
--no-handle-help
--no-handle-version
if --no-handle-help (--no-handle-version) is given the command line option --help|-h (--version|-V) is not handled automatically, so the programmer will be able to print some other information; then the function for printing the standard help (version) response can be used; this function is called <parser-name>_print_help (<parser-name>_print_version), where <parser-name> is the name specified with --func-name or the default, cmdline_parser.
--no-handle-error
if --no-handle-error is given, an error in the parsing does not provoke the exit of the program; instead, since the parser function, in case of an error, returns a value different 0, the program can print a help message, as gengetopt itself does in case of an error (try it!).
--gen-version
is a flag (default on) that when disabled does not put in the output file the gengetopt version (it is useful for testing purposes).

You may have already guessed it: gengetopt uses gengetopt itself for command line options, and its specification file is cmdline.ggo in the source directory. In particular the command line for gengetopt itself is generated with the following command:

     gengetopt --input=cmdline.ggo --no-handle-version \
               --no-handle-help --no-handle-error

Indeed when --help|-h is passed on the command line, gengetopt will call cmdline_parser_print_help() and then the lines for reporting bugs. When --version|-V is passed, it will call cmdline_parser_print_version() and then prints a copyright. If an error occurs it prints a message on the screen:

     $ ./gengetopt --zzzz
     ./gengetopt: unrecognized option `--zzzz'
     Run gengetopt --help to see the list of options.


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4 Terminology

An argument is an element of the argv array passed into your C or C++ program by your operating system.

An option is an argument that begins with -, or --.

A value is an argument, or part of an argument, that is associated with a particular option (an option may also not accept any value). For example, in

     > ls --width=80

ls is called with one argument, --width=80, which is an option that has a value, 80, while in

     > ls --width 80

ls is called with two arguments, --width, which is an option, and 80 which might or might not be a value. In this case, whether the 80 is treated as a value associated with the preceding --width option, or as the name of a file to list depends on how ls parses the --width option.

The order in which options are specified is usually unimportant:

     > ls -a -l
     > ls -l -a

both do exactly the same thing.

An parameter is an argument that is not an option. For example, in

     > cp --archive source dest

cp is called with three arguments, the option --archive, the parameter source, and the parameter dest. Unlike options, the order in which parameters are specified usually is important:

     > cp --archive --verbose source dest
     > cp --verbose --archive source dest
     > cp --archive source --verbose dest
     > cp --archive --verbose dest source

The first three cp commands do the same thing, but the fourth one is completely different.

If you're new to Gengetopt, you may wish to skip the rest of this section. It goes into more detail about different sorts of options, and how they are parsed.

Note that some parameters may begin with - or --. Equivalently, not all arguments that begin with - or -- are options. Consider

     > ls -- -file
     > tar -c -f - . > ../foo.tar

The ls command has two arguments; the first argument, -- is ignored by ls, but causes the -file argument to be interpreted as a parameter. The tar command has four arguments. The -c argument tells tar to create an archive; the -f argument, which takes a value, -, tells tar that the archive should be written onto the standard output, and the fourth argument, ., tells tar what directories to include in the archive. (The remaining two items, > and ../foo.tar, tell the shell to redirect the tar command's output to the file ../foo.tar. The tar command doesn't even see them.)

The GNU convention is that - by itself is always interpreted as a value or parameter, while the first -- by itself is always ignored, but causes all subsequent arguments to be interpreted as parameters. Gengetopt always behaves this way.

A short option is an option that begins with -. Not including the leading dash, short options must be one character long:

     > ls -a -l -t --width=80

The -a, -l, and -t options are all short options. Multiple short options may be combined into a single argument:

     > ls -alt --width=80

is equivalent to the above example.

A long option is an option that begins with - or --. Ignoring the leading punctuation, long options may be one or more characters long:

     > ls --all -fs

The ls command has two arguments; the long option --all, and the pair of short options -fs.

Long options need not have synonymous short options; after all, complex programs like cc have more long options than there are valid short option characters; it wouldn't be possible to assign a short option to each of them. Short options are encouraged, but not required, to have a synonymous long option.

Long options may be abbreviated, as long as the abbreviation is not ambiguous. Gengetopt automatically treats unambiguous abbreviations as synonyms.

Short options may have values just like long options, but if several short options are grouped together into one argument, only the last one may have a value. Values in the same argument as a long option are delimited by an equals sign, values in the same argument as a short option are not:

     > ls --width 60  # ok, value is "60"
     > ls --width=60  # ok, value is "60"
     > ls -w60        # ok, value is "60"
     > ls -w 60       # ok, value is "60"
     > ls -w=60       # unexpected, value is "=60"
     > ls -T7 -w60    # ok, value for -T is 7, value for -w is 60
     > ls -T7w60      # unexpected, value for -T is "7w60", no -w at all

A required option must be present, otherwise an error will be raised.

A multiple option is an option that may appear more than once on the command line. Gengetopt would create a tidy array for multiple options (see Multiple Options, for further details about dealing with multiple options).


Next: , Previous: Terminology, Up: Top

5 Group options

It is also possible to group options; options belonging to a group are considered in mutual exclusion. In order to use this feature, first the group has to be defined, and then a groupoption can be defined. A groupoption has basically the same syntax of a standard option, apart that the required flag must not be specified (it would not make sense, since the options of the same group are mutual exclusive) and the group to which the option belongs has to be specified.

     defgroup "<group name>" {groupdesc="<group description>"} {yes}
     groupoption <long> <short> <desc> <argtype> group="<group name>" \
          {argoptional} {multiple}

If a group is defined as required, then one (but only one) option belonging to the group has to be specified.

Here's an example (taken from the test test_group_cmd.ggo):

     defgroup "my grp2"
     defgroup "grp1" groupdesc="an option of this group is required" yes
     groupoption "opta" a "string a" group="grp1" multiple
     groupoption "optA" A "string A" string group="grp1" argoptional
     groupoption "optAmul" M "string M" string group="grp1" argoptional multiple
     groupoption "optb" b "string b" group="grp1"
     groupoption "optc" - "string c" group="my grp2"
     groupoption "optd" d "string d" group="my grp2"

The group grp1 is required, so either --opta or --optb has to be specified (but only one of them). Here's the output of some executions:

     $ ./test_groups
     test_groups: 0 options of group grp1 were given. One is required
     $ ./test_groups -a          OK
     $ ./test_groups -a -a       OK (the same option given twice)
     $ ./test_groups -a -b
     test_groups: 2 options of group grp1 were given. One is required
     $ ./test_groups -a -c       OK
     $ ./test_groups -a --optc -d
     test_groups: 2 options of group my grp2 were given. At most one is required


Next: , Previous: Group options, Up: Top

6 Configuration files

It is often useful to specify command line options directly in a configuration file, so that the value of some options are read from this file if they are not given as command line options. When the command line option --conf-parser is given to gengetopt, apart from the standard command line option parser, also this additional parser is generated (its name is <commandline_parser>_configfile):

     int
     <cmd_parser_name>_configfile (char * const filename,
                                   struct gengetopt_args_info *args_info,
                                   int override,
                                   int initialize,
                                   int check_required);

The parameter override tells whether the values read in the configuration file have to override those specified at the command line. The initialize tells whether the args_info struct has to be initialize.

IMPORTANT: you have to explicitly set initialize to true (i.e., different from 0) if you call the config file parser before the standard command line option parser, otherwise unpredictable results may show.

The check_required tells whether the check for required options must be performed or not.

If you call the config file parser before the standard command line option parser and then you want to call the standard command line parser you MUST use this second version, passing 0 for initialized, so that collected values from the config file are not lost:

     int
     <cmd_parser_name>2 (int argc,
                         char * const *argv,
                         struct gengetopt_args_info *args_info,
                         int override,
                         int initialize,
                         int check_required);

Notice, that with this version you can also specify whether the options passed at the command line must override the ones read from the config file. If you set override to 0, and a command line option is given that has already been read from the config file, an error will be raised. Moreover, you have to specify whether the check for missing required options must be performed or not. This concerns also options of a required group (Group options).

If you decide not to request the check for required option, you can test it manually, after the command line parsing returns by using the following generated function:

     int
     <cmd_parser_name>_required (struct gengetopt_args_info *args_info,
                                 const char *program_name);

where program_name is the name of your executable (usually you should pass argv[0] as argument). If the function returns a value different from 0, then some required options are missing. An error has already been printed by this function. This concerns also options of a required group (Group options).

The config file has the following simple syntax: lines starting with # are considered comments and:

     <option_name> = {<option_val>}

or simply (if the option does not take an argument):

     <option_name>

which means that option_name is given, and if it accepts an argument, then its value is option_val. The = is not mandatory.

For instance here's a program that uses this feature (this is the test test_conf_parser):

     /* test_conf_parser.c test */
     
     /* test all kinds of options and the conf file parser */
     
     #include <stdlib.h>
     #include <stdio.h>
     
     #include "test_conf_parser_cmd.h"
     
     static struct my_args_info args_info;
     
     int
     main (int argc, char **argv)
     {
       int i;
       int result = 0;
     
       if (test_conf_parser_cmd_parser (argc, argv, &args_info) != 0) {
         result = 1;
         goto stop;
       }
     
       /* override cmd options, but do not initialize args_info, check for required options */
       if (test_conf_parser_cmd_parser_configfile
           (args_info.conf_file_arg, &args_info, 1, 0, 1) != 0)
         {
           result = 1;
           goto stop;
         }
     
       printf ("value of required: %s\n", args_info.required_arg);
       printf ("value of string: %s\n", args_info.string_arg);
       printf ("value of no-short_given: %d\n", args_info.no_short_given);
       printf ("value of int: %d\n", args_info.int_arg);
       printf ("value of float: %f\n", args_info.float_arg);
     
       printf ("value of multi-string_given: %d\n", args_info.multi_string_given);
       for (i = 0; i < args_info.multi_string_given; ++i)
         printf ("  value of multi-string: %s\n", args_info.multi_string_arg [i]);
     
       printf ("value of multi-string-def_given: %d\n",
               args_info.multi_string_def_given);
       for (i = 0; i < args_info.multi_string_def_given; ++i)
         printf ("  value of multi-string-def: %s\n",
                 args_info.multi_string_def_arg [i]);
       if (!args_info.multi_string_def_given && args_info.multi_string_def_arg [0])
         printf ("default value of multi-string-def: %s\n",
                 args_info.multi_string_def_arg [0]);
     
       printf ("value of opta: %s\n", args_info.opta_arg);
     
       printf ("noarg given %d times\n", args_info.noarg_given);
       printf ("noarg_noshort given %d times\n", args_info.noarg_noshort_given);
     
       printf ("opt-arg given: %d\n", args_info.opt_arg_given);
       printf ("opt-arg value: %s\n", (args_info.opt_arg_arg ? args_info.opt_arg_arg : "not given"));
     
       if (args_info.file_save_given) {
         if (test_conf_parser_cmd_parser_file_save (args_info.file_save_arg, &args_info) == EXIT_FAILURE)
           result = 1;
         else
           printf ("saved configuration file %s\n", args_info.file_save_arg);
       }
     
      stop:
       test_conf_parser_cmd_parser_free (&args_info);
     
       return result;
     }
     

So if we use the following config file

     # required option
     required "this is a test"
     float 3.14
     no-short
     string another

and we run test_conf_parser like that, we will have

     ./test_conf_parser -r bar -i 100 --float 2.14 --conf-file test_conf.conf
     value of required: this is a test
     value of string: another
     value of no-short: 1
     value of int: 100
     value of float: 3.140000

If, instead we call the test_conf_parser_cmd_parser_configfile with 0 for override argument, we get the following result

     value of required: bar
     value of string: another
     value of no-short: 1
     value of int: 100
     value of float: 2.140000

This second example use the second version of the command line parser: first call the configuration file parser and then the command line parser (the command line options will override the configuration file options):

     /* test_conf_parser_ov2.c test */
     
     /* test all kinds of options and the conf file parser */
     /* differently from test_conf_parser_ov.c, first scan the conf file and
        then the command line */
     
     #include <stdlib.h>
     #include <stdio.h>
     
     #include "test_conf_parser_cmd.h"
     
     static struct my_args_info args_info;
     
     int
     main (int argc, char **argv)
     {
       /* do not override command line options, initialize args_info */
       if (test_conf_parser_cmd_parser_configfile
           ("./test_conf2.conf", &args_info, 0, 1, 0) != 0)
         exit(1);
     
       if (test_conf_parser_cmd_parser2 (argc, argv, &args_info, 1, 0, 1) != 0)
         exit(1) ;
     
       printf ("value of required: %s\n", args_info.required_arg);
       printf ("value of string: %s\n", args_info.string_arg);
       printf ("value of no-short_given: %d\n", args_info.no_short_given);
       printf ("value of int: %d\n", args_info.int_arg);
       printf ("value of float: %f\n", args_info.float_arg);
     
       test_conf_parser_cmd_parser_free (&args_info);
     
       return 0;
     }
     

This is an invocation and its results:

     ./test_conf_parser_ov2 -r "bar" --float 2.14 -i 100
     value of required: bar
     value of string: another
     value of no-short: 1
     value of int: 100
     value of float: 2.140000

6.1 Further details on the configuration file parser

The generated config file parser function uses the constant CONFIG_FILE_LINE_SIZE to read each line of the configuration file. By default this constant is set to 2048 that should be enough for most applications. If your application uses configuration files with lines that are longer, you can compile the generated C file by specifying an explicit value for this constant with the -D command line option of gcc.


Next: , Previous: Configuration files, Up: Top

7 Multiple Options

If an option is specified as multiple, then it can be specified multiple times at command line. In this case, say the option is called foo, the generated foo_given field in the args structure contains the number of times it was specified and the generated field foo_arg is an array containing all the values that were specified for this option.

Notice that if a default value is specified for a multiple option, that value is assigned to the option only if no other value is specified on the command line (and the corresponding _given field will be set to 1), i.e., a default value IS NOT always part of the values of a multiple option.

For instance, if the gengetopt file is as follows

     # test options that can be given more than once
     option "string"      s "string option" string no multiple
     option "int"         i "int option" int no multiple

Then the command line options can be collected like that

     

Then if this program is called with the following command line options

     /* test options that can be given more than once */
     
     #include <stdlib.h>
     #include <stdio.h>
     
     #include "test_multiple_cmd.h"
     
     static struct gengetopt_args_info args_info;
     
     int
     main (int argc, char **argv)
     {
       int i = 0;
     
       if (test_multiple_cmd_parser (argc, argv, &args_info) != 0)
         exit(1) ;
     
       for (i = 0; i < args_info.string_given; ++i)
         printf ("passed string: %s\n", args_info.string_arg[i]);
     
       for (i = 0; i < args_info.int_given; ++i)
         printf ("passed int: %d\n", args_info.int_arg[i]);
     
       return 0;
     }
     

The output of the program will be

     passed string: world
     passed string: hello
     passed string: bar
     passed string: foo
     passed int: 200
     passed int: 100

You can also pass arguments to a multiple option separated by commas, as in the following:

     ./test_multiple -s"foo","bar","hello" -i100,200 -s "world"


Next: , Previous: Multiple Options, Up: Top

8 What if getopt_long is not available?

If you use gengetopt to generate C functions for parsing command line arguments you have to know that these generated functions use getopt_long to actually read the command line and parsing it. This function is typically part of the standard C library, but some implementations may not include it. But this is not a problem: we provide C files that actually implement getopt_long function: getopt.c getopt1.c and gnugetopt.h. You'll find these files in the <install prefix>/share/gengetopt directory where <install prefix> is the one you specified during compilation. If no prefix had been specified, /usr/local is the default. If you downloaded gengetopt in binary form prefix will probably be /usr/local or /usr.

You can rename gnugetopt.h to getopt.h and then simply compile these files and link them to the executable of you program. However, if you use automake and autoconf here's a more elegant solution: you should download the macro you find at this URL:

http://www.gnu.org/software/ac-archive/m4source/adl_func_getopt_long.m4

and add it to your acinclude.m4. You can find this macro also in the acinclude.m4 in the sources of gengetopt.

This macro checks if getopt_long function is in C library; if it is not then it adds getopt.o and getopt1.o to the objects files that will be linked to your executable (LIBOBJS).

Then in Makefile.am of your source directory you have to add the contents of LIBOBJS to the LDADD of the program that has to use getopt_long; e.g., if the program foo has to use getopt_long, you have to add the following line

     foo_LDADD = @LIBOBJS@

Now these files will be compiled and linked to your program only if necessary.

Moreover you have to add getopt.c getopt1.c and gnugetopt.h to your distribution. Note that it is not necessary to put these file names among the foo_SOURCES contents), but you have to add gnugetopt.h to EXTRA_DIST:

     EXTRA_DIST = gnugetopt.h

You may want to take a look at gengetopt's configure.in and src/Makefile.am: they both use the techniques described here.


Next: , Previous: No getopt_long, Up: Top

9 Known Bugs and Limitations

If you find a bug in gengetopt, please send electronic mail to

bug-gengetopt at gnu dot org

Include the version number, which you can find by running gengetopt --version. Also include in your message the output that the program produced and the output you expected.

If you have other questions, comments or suggestions about gengetopt, contact the author via electronic mail (find the address at http://www.lorenzobettini.it). The author will try to help you out, although he may not have time to fix your problems.

The list of todos in the TODO.


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10 Mailing Lists

The following mailing lists are available:

help-gengetopt at gnu dot org

for generic discussions about the program and for asking for help about it (open mailing list), http://mail.gnu.org/mailman/listinfo/help-gengetopt

info-gengetopt at gnu dot org

for receiving information about new releases and features (read-only mailing list), http://mail.gnu.org/mailman/listinfo/info-gengetopt.

If you want to subscribe to a mailing list just go to the URL and follow the instructions, or send me an e-mail and I'll subscribe you.


Previous: Mailing Lists, Up: Top

Index

Table of Contents


Footnotes

[1] Command lines that are too long are split into multiple indented lines separated by a \. Of course these commands are to be given in one line only, anyway.

[2] The <option>_orig was introduced in the release 2.14.

[3] This function was introduced in the release 2.14.