Commandline option parser

Commandline option parser — parses commandline options

Synopsis


#include <glib.h>


enum        GOptionError;
#define     G_OPTION_ERROR
gboolean    (*GOptionArgFunc)               (const gchar *option_name,
                                             const gchar *value,
                                             gpointer data,
                                             GError **error);
            GOptionContext;
GOptionContext* g_option_context_new        (const gchar *parameter_string);
void        g_option_context_free           (GOptionContext *context);
gboolean    g_option_context_parse          (GOptionContext *context,
                                             gint *argc,
                                             gchar ***argv,
                                             GError **error);
void        g_option_context_set_help_enabled
                                            (GOptionContext *context,
                                             gboolean help_enabled);
gboolean    g_option_context_get_help_enabled
                                            (GOptionContext *context);
void        g_option_context_set_ignore_unknown_options
                                            (GOptionContext *context,
                                             gboolean ignore_unknown);
gboolean    g_option_context_get_ignore_unknown_options
                                            (GOptionContext *context);
enum        GOptionArg;
enum        GOptionFlags;
#define     G_OPTION_REMAINING
            GOptionEntry;
void        g_option_context_add_main_entries
                                            (GOptionContext *context,
                                             const GOptionEntry *entries,
                                             const gchar *translation_domain);
            GOptionGroup;
void        g_option_context_add_group      (GOptionContext *context,
                                             GOptionGroup *group);
void        g_option_context_set_main_group (GOptionContext *context,
                                             GOptionGroup *group);
GOptionGroup* g_option_context_get_main_group
                                            (GOptionContext *context);
GOptionGroup* g_option_group_new            (const gchar *name,
                                             const gchar *description,
                                             const gchar *help_description,
                                             gpointer user_data,
                                             GDestroyNotify destroy);
void        g_option_group_free             (GOptionGroup *group);
void        g_option_group_add_entries      (GOptionGroup *group,
                                             const GOptionEntry *entries);
gboolean    (*GOptionParseFunc)             (GOptionContext *context,
                                             GOptionGroup *group,
                                             gpointer data,
                                             GError **error);
void        g_option_group_set_parse_hooks  (GOptionGroup *group,
                                             GOptionParseFunc pre_parse_func,
                                             GOptionParseFunc post_parse_func);
void        (*GOptionErrorFunc)             (GOptionContext *context,
                                             GOptionGroup *group,
                                             gpointer data,
                                             GError **error);
void        g_option_group_set_error_hook   (GOptionGroup *group,
                                             GOptionErrorFunc error_func);
const gchar* (*GTranslateFunc)              (const gchar *str,
                                             gpointer data);
void        g_option_group_set_translate_func
                                            (GOptionGroup *group,
                                             GTranslateFunc func,
                                             gpointer data,
                                             GDestroyNotify destroy_notify);
void        g_option_group_set_translation_domain
                                            (GOptionGroup *group,
                                             const gchar *domain);

Description

The GOption commandline parser is intended to be a simpler replacement for the popt library. It supports short and long commandline options, as shown in the following example:

testtreemodel -r 1 --max-size 20 --rand --display=:1.0 -vb -- file1 file2

The example demonstrates a number of features of the GOption commandline parser

  • Options can be single letters, prefixed by a single dash. Multiple short options can be grouped behind a single dash.

  • Long options are prefixed by two consecutive dashes.

  • Options can have an extra argument, which can be a number, a string or a filename. For long options, the extra argument can be appended with an equals sign after the option name.

  • Non-option arguments are returned to the application as rest arguments.

  • An argument consisting solely of two dashes turns off further parsing, any remaining arguments (even those starting with a dash) are returned to the application as rest arguments.

Another important feature of GOption is that it can automatically generate nicely formatted help output. Unless it is explicitly turned off with g_option_context_set_help_enabled(), GOption will recognize the --help, -?, --help-all and --help-groupname options (where groupname is the name of a GOptionGroup) and write a text similar to the one shown in the following example to stdout.

Usage:
  testtreemodel [OPTION...] - test tree model performance

Help Options:
  -?, --help               Show help options
  --help-all               Show all help options
  --help-gtk               Show GTK+ Options

Application Options:
  -r, --repeats=N          Average over N repetitions
  -m, --max-size=M         Test up to 2^M items
  --display=DISPLAY        X display to use
  -v, --verbose            Be verbose
  -b, --beep               Beep when done   
  --rand                   Randomize the data

GOption groups options in GOptionGroups, which makes it easy to incorporate options from multiple sources. The intended use for this is to let applications collect option groups from the libraries it uses, add them to their GOptionContext, and parse all options by a single call to g_option_context_parse(). See gtk_get_option_group() for an example.

If an option is declared to be of type string or filename, GOption takes care of converting it to the right encoding; strings are returned in UTF-8, filenames are returned in the GLib filename encoding.

Here is a complete example of setting up GOption to parse the example commandline above and produce the example help output.

static gint repeats = 2;
static gint max_size = 8;
static gboolean verbose = FALSE;
static gboolean beep = FALSE;
static gboolean rand = FALSE;

static GOptionEntry entries[] = 
{
  { "repeats", 'r', 0, G_OPTION_ARG_INT, &repeats, "Average over N repetitions", "N" },
  { "max-size", 'm', 0, G_OPTION_ARG_INT, &max_size, "Test up to 2^M items", "M" },
  { "verbose", 'v', 0, G_OPTION_ARG_NONE, &verbose, "Be verbose", NULL },
  { "beep", 'b', 0, G_OPTION_ARG_NONE, &beep, "Beep when done", NULL },
  { "rand", 0, 0, G_OPTION_ARG_NONE, &rand, "Randomize the data", NULL },
  { NULL }
};

int 
main (int argc, char *argv[])
{
  GError *error = NULL;

  context = g_option_context_new ("- test tree model performance");
  g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
  g_option_context_add_group (context, gtk_get_option_group (TRUE));
  g_option_context_parse (context, &argc, &argv, &error);
  
  /* ... */

}

Details

enum GOptionError

typedef enum
{
  G_OPTION_ERROR_UNKNOWN_OPTION,
  G_OPTION_ERROR_BAD_VALUE,
  G_OPTION_ERROR_FAILED
} GOptionError;

Error codes returned by option parsing.

G_OPTION_ERROR_UNKNOWN_OPTION An option was not known to the parser. This error will only be reported, if the parser hasn't been instructed to ignore unknown options, see g_option_context_set_ignore_unknown_options().
G_OPTION_ERROR_BAD_VALUE A value couldn't be parsed.
G_OPTION_ERROR_FAILED A GOptionArgFunc callback failed.

G_OPTION_ERROR

#define G_OPTION_ERROR (g_option_error_quark ())

Error domain for option parsing. Errors in this domain will be from the GOptionError enumeration. See GError for information on error domains.


GOptionArgFunc ()

gboolean    (*GOptionArgFunc)               (const gchar *option_name,
                                             const gchar *value,
                                             gpointer data,
                                             GError **error);

The type of function to be passed as callback for G_OPTION_ARG_CALLBACK options.

option_name : The name of the option being parsed. This will be either a single dash followed by a single letter (for a short name) or two dashes followed by a long option name.
value : The value to be parsed.
data : User data added to the GOptionGroup containing the option when it was created with g_option_group_new()
error : A return location for errors. The error code G_OPTION_ERROR_FAILED is intended to be used for errors in GOptionArgFunc callbacks.
Returns : TRUE if the option was successfully parsed, FALSE if an error occurred

GOptionContext

typedef struct _GOptionContext GOptionContext;

A GOptionContext struct defines which options are accepted by the commandline option parser. The struct has only private fields and should not be directly accessed.


g_option_context_new ()

GOptionContext* g_option_context_new        (const gchar *parameter_string);

Creates a new option context.

parameter_string : a string which is displayed in the first line of --help output, after programname [OPTION...]
Returns : a newly created GOptionContext, which must be freed with g_option_context_free() after use.

Since 2.6


g_option_context_free ()

void        g_option_context_free           (GOptionContext *context);

Frees context and all the groups which have been added to it.

context : a GOptionContext

Since 2.6


g_option_context_parse ()

gboolean    g_option_context_parse          (GOptionContext *context,
                                             gint *argc,
                                             gchar ***argv,
                                             GError **error);

Parses the command line arguments, recognizing options which have been added to context. A side-effect of calling this function is that g_set_prgname() will be called.

If the parsing is successful, any parsed arguments are removed from the array and argc and argv are updated accordingly. A '--' option is stripped from argv unless there are unparsed options before and after it, or some of the options after it start with '-'. In case of an error, argc and argv are left unmodified.

If automatic --help support is enabled (see g_option_context_set_help_enabled()), and the argv array contains one of the recognized help options, this function will produce help output to stdout and call exit (0).

context : a GOptionContext
argc : a pointer to the number of command line arguments.
argv : a pointer to the array of command line arguments.
error : a return location for errors
Returns : TRUE if the parsing was successful, FALSE if an error occurred

Since 2.6


g_option_context_set_help_enabled ()

void        g_option_context_set_help_enabled
                                            (GOptionContext *context,
                                             gboolean help_enabled);

Enables or disables automatic generation of --help output. By default, g_option_context_parse() recognizes --help, -?, --help-all and --help-groupname and creates suitable output to stdout.

context : a GOptionContext
help_enabled : TRUE to enable --help, FALSE to disable it

Since 2.6


g_option_context_get_help_enabled ()

gboolean    g_option_context_get_help_enabled
                                            (GOptionContext *context);

Returns whether automatic --help generation is turned on for context. See g_option_context_set_help_enabled().

context : a GOptionContext
Returns : TRUE if automatic help generation is turned on.

Since 2.6


g_option_context_set_ignore_unknown_options ()

void        g_option_context_set_ignore_unknown_options
                                            (GOptionContext *context,
                                             gboolean ignore_unknown);

Sets whether to ignore unknown options or not. If an argument is ignored, it is left in the argv array after parsing. By default, g_option_context_parse() treats unknown options as error.

This setting does not affect non-option arguments (i.e. arguments which don't start with a dash). But note that GOption cannot reliably determine whether a non-option belongs to a preceding unknown option.

context : a GOptionContext
ignore_unknown : TRUE to ignore unknown options, FALSE to produce an error when unknown options are met

Since 2.6


g_option_context_get_ignore_unknown_options ()

gboolean    g_option_context_get_ignore_unknown_options
                                            (GOptionContext *context);

Returns whether unknown options are ignored or not. See g_option_context_set_ignore_unknown_options().

context : a GOptionContext
Returns : TRUE if unknown options are ignored.

Since 2.6


enum GOptionArg

typedef enum
{
  G_OPTION_ARG_NONE,
  G_OPTION_ARG_STRING,
  G_OPTION_ARG_INT,
  G_OPTION_ARG_CALLBACK,
  G_OPTION_ARG_FILENAME,
  G_OPTION_ARG_STRING_ARRAY,
  G_OPTION_ARG_FILENAME_ARRAY
} GOptionArg;

The GOptionArg enum values determine which type of extra argument the options expect to find. If an option expects an extra argument, it can be specified in several ways; with a short option: -x arg, with a long option: --name arg or combined in a single argument: --name=arg.

G_OPTION_ARG_NONE No extra argument. This is useful for simple flags.
G_OPTION_ARG_STRING The option takes a string argument.
G_OPTION_ARG_INT The option takes an integer argument.
G_OPTION_ARG_CALLBACK The option provides a callback to parse the extra argument.
G_OPTION_ARG_FILENAME The option takes a filename as argument.
G_OPTION_ARG_STRING_ARRAY The option takes a string argument, multiple uses of the option are collected into an array of strings.
G_OPTION_ARG_FILENAME_ARRAY The option takes a filename as argument, multiple uses of the option are collected into an array of strings.

enum GOptionFlags

typedef enum
{
  G_OPTION_FLAG_HIDDEN       = 1 << 0,
  G_OPTION_FLAG_IN_MAIN      = 1 << 1,
  G_OPTION_FLAG_REVERSE	     = 1 << 2
} GOptionFlags;

Flags which modify individual options.

G_OPTION_FLAG_HIDDEN The option doesn't appear in --help output.
G_OPTION_FLAG_IN_MAIN The option appears in the main section of the --help output, even if it is defined in a group.
G_OPTION_FLAG_REVERSE For options of the G_OPTION_ARG_NONE kind, this flag indicates that the sense of the option is reversed.

G_OPTION_REMAINING

#define G_OPTION_REMAINING ""

If a long option in the main group has this name, it is not treated as a regular option. Instead it collects all non-option arguments which would otherwise be left in argv. The option must be of type G_OPTION_ARG_STRING_ARRAY or G_OPTION_ARG_FILENAME_ARRAY.

Using G_OPTION_REMAINING instead of simply scanning argv for leftover arguments has the advantage that GOption takes care of necessary encoding conversions for strings or filenames.

Since 2.6


GOptionEntry

typedef struct {
  const gchar *long_name;
  gchar        short_name;
  gint         flags;

  GOptionArg   arg;
  gpointer     arg_data;
  
  const gchar *description;
  const gchar *arg_description;
} GOptionEntry;

A GOptionEntry defines a single option. To have an effect, they must be added to a GOptionGroup with g_option_context_add_main_entries() or g_option_group_add_entries().

const gchar *long_name; The long name of an option can be used to specify it in a commandline as --long_name. Every option must have a long name. To resolve conflicts if multiple option groups contain the same long name, it is also possible to specify the option as --groupname-long_name.
gchar short_name; If an option has a short name, it can be specified -short_name in a commandline.
gint flags; Flags from GOptionFlags.
GOptionArg arg; The type of the option, as a GOptionArg.
gpointer arg_data; If the arg type is G_OPTION_ARG_CALLBACK, then arg_data must point to a GOptionArgFunc callback function, which will be called to handle the extra argument. Otherwise, arg_data is a pointer to a location to store the value, the required type of the location depends on the arg type:
G_OPTION_ARG_NONE

gboolean

G_OPTION_ARG_STRING

gchar*

G_OPTION_ARG_INT

gint

G_OPTION_ARG_FILENAME

gchar*

G_OPTION_ARG_STRING_ARRAY

gchar**

G_OPTION_ARG_FILENAME_ARRAY

gchar**

const gchar *description; the description for the option in --help output. The description is translated using the translate_func of the group, see g_option_group_set_translation_domain().
const gchar *arg_description; The placeholder to use for the extra argument parsed by the option in --help output. The arg_description is translated using the translate_func of the group, see g_option_group_set_translation_domain().

g_option_context_add_main_entries ()

void        g_option_context_add_main_entries
                                            (GOptionContext *context,
                                             const GOptionEntry *entries,
                                             const gchar *translation_domain);

A convenience function which creates a main group if it doesn't exist, adds the entries to it and sets the translation domain.

context : a GOptionContext
entries : a NULL-terminated array of GOptionEntrys
translation_domain : a translation domain to use for translating the --help output for the options in entries with gettext(), or NULL

Since 2.6


GOptionGroup

typedef struct _GOptionGroup GOptionGroup;

A GOptionGroup struct defines the options in a single group. The struct has only private fields and should not be directly accessed.

All options in a group share the same translation function. Libaries which need to parse commandline options are expected to provide a function for getting a GOptionGroup holding their options, which the application can then add to its GOptionContext.


g_option_context_add_group ()

void        g_option_context_add_group      (GOptionContext *context,
                                             GOptionGroup *group);

Adds a GOptionGroup to the context, so that parsing with context will recognize the options in the group. Note that the group will be freed together with the context when g_option_context_free() is called, so you must not free the group yourself after adding it to a context.

context : a GOptionContext
group : the group to add

Since 2.6


g_option_context_set_main_group ()

void        g_option_context_set_main_group (GOptionContext *context,
                                             GOptionGroup *group);

Sets a GOptionGroup as main group of the context. This has the same effect as calling g_option_context_add_group(), the only difference is that the options in the main group are treated differently when generating --help output.

context : a GOptionContext
group : the group to set as main group

Since 2.6


g_option_context_get_main_group ()

GOptionGroup* g_option_context_get_main_group
                                            (GOptionContext *context);

Returns a pointer to the main group of context.

context : a GOptionContext
Returns : the main group of context, or NULL if context doesn't have a main group. Note that group belongs to context and should not be modified or freed.

Since 2.6


g_option_group_new ()

GOptionGroup* g_option_group_new            (const gchar *name,
                                             const gchar *description,
                                             const gchar *help_description,
                                             gpointer user_data,
                                             GDestroyNotify destroy);

Creates a new GOptionGroup.

name : the name for the option group, this is used to provide help for the options in this group with --help-name
description : a description for this group to be shown in --help. This string is translated using the translation domain or translation function of the group
help_description : a description for the --help-name option. This string is translated using the translation domain or translation function of the group
user_data : user data that will be passed to the pre- and post-parse hooks, the error hook and to callbacks of G_OPTION_ARG_CALLBACK options, or NULL
destroy : a function that will be called to free user_data, or NULL
Returns : a newly created option group. It should be added to a GOptionContext or freed with g_option_group_free().

Since 2.6


g_option_group_free ()

void        g_option_group_free             (GOptionGroup *group);

Frees a GOptionGroup. Note that you must not free groups which have been added to a GOptionContext.

group : a GOptionGroup

Since 2.6


g_option_group_add_entries ()

void        g_option_group_add_entries      (GOptionGroup *group,
                                             const GOptionEntry *entries);

Adds the options specified in entries to group.

group : a GOptionGroup
entries : a NULL-terminated array of GOptionEntrys

Since 2.6


GOptionParseFunc ()

gboolean    (*GOptionParseFunc)             (GOptionContext *context,
                                             GOptionGroup *group,
                                             gpointer data,
                                             GError **error);

The type of function that can be called before and after parsing.

context The active GOptionContext
context :
group : The group to which the function belongs
data : User data added to the GOptionGroup containing the option when it was created with g_option_group_new()
error : A return location for error details
Returns : TRUE if the function completed successfully, FALSE if an error occurred

g_option_group_set_parse_hooks ()

void        g_option_group_set_parse_hooks  (GOptionGroup *group,
                                             GOptionParseFunc pre_parse_func,
                                             GOptionParseFunc post_parse_func);

Associates two functions with group which will be called from g_option_context_parse() before the first option is parsed and after the last option has been parsed, respectively.

Note that the user data to be passed to pre_parse_func and post_parse_func can be specified when constructing the group with g_option_group_new().

group : a GOptionGroup
pre_parse_func : a function to call before parsing, or NULL
post_parse_func : a function to call after parsing, or NULL

Since 2.6


GOptionErrorFunc ()

void        (*GOptionErrorFunc)             (GOptionContext *context,
                                             GOptionGroup *group,
                                             gpointer data,
                                             GError **error);

The type of function to be used as callback when a parse error occurs.

context The active GOptionContext
context :
group : The group to which the function belongs
data : User data added to the GOptionGroup containing the option when it was created with g_option_group_new()
error : The GError containing details about the parse error

g_option_group_set_error_hook ()

void        g_option_group_set_error_hook   (GOptionGroup *group,
                                             GOptionErrorFunc error_func);

Associates a function with group which will be called from g_option_context_parse() when an error occurs.

Note that the user data to be passed to pre_parse_func and post_parse_func can be specified when constructing the group with g_option_group_new().

group : a GOptionGroup
error_func : a function to call when an error occurs

Since 2.6


GTranslateFunc ()

const gchar* (*GTranslateFunc)              (const gchar *str,
                                             gpointer data);

The type of functions which are used to translate user-visible strings, for --help output.

str : the untranslated string
data : user data specified when installing the function, e.g. in g_option_group_set_translate_func()
Returns : a translation of the string for the current locale. The returned string is owned by GLib and must not be freed.

g_option_group_set_translate_func ()

void        g_option_group_set_translate_func
                                            (GOptionGroup *group,
                                             GTranslateFunc func,
                                             gpointer data,
                                             GDestroyNotify destroy_notify);

Sets the function which is used to translate user-visible strings, for --help output. Different groups can use different GTranslateFuncs. If func is NULL, strings are not translated.

If you are using gettext(), you only need to set the translation domain, see g_option_group_set_translation_domain().

group : a GOptionGroup
func : the GTranslateFunc, or NULL
data : user data to pass to func, or NULL
destroy_notify : a function which gets called to free data, or NULL

Since 2.6


g_option_group_set_translation_domain ()

void        g_option_group_set_translation_domain
                                            (GOptionGroup *group,
                                             const gchar *domain);

A convenience function to use gettext() for translating user-visible strings.

group : a GOptionGroup
domain : the domain to use

Since 2.6