GApplicationCommandLine: GIO Reference Manual

GApplicationCommandLine

GApplicationCommandLine — A command-line invocation of an application

Functions

Properties

GVariant *	arguments	Write / Construct Only
gboolean	is-remote	Read
GVariant *	options	Write / Construct Only
GVariant *	platform-data	Write / Construct Only

Types and Values

	GApplicationCommandLine
struct	GApplicationCommandLineClass

Object Hierarchy

    GObject
    ╰── GApplicationCommandLine

Includes

#include <gio/gio.h>

Description

GApplicationCommandLine represents a command-line invocation of an application. It is created by GApplication and emitted in the “command-line” signal and virtual function.

The class contains the list of arguments that the program was invoked with. It is also possible to query if the commandline invocation was local (ie: the current process is running in direct response to the invocation) or remote (ie: some other process forwarded the commandline to this process).

The GApplicationCommandLine object can provide the argc and argv parameters for use with the GOptionContext command-line parsing API, with the g_application_command_line_get_arguments() function. See gapplication-example-cmdline3.c for an example.

The exit status of the originally-invoked process may be set and messages can be printed to stdout or stderr of that process. The lifecycle of the originally-invoked process is tied to the lifecycle of this object (ie: the process exits when the last reference is dropped).

The main use for GApplicationCommandLine (and the “command-line” signal) is 'Emacs server' like use cases: You can set the EDITOR environment variable to have e.g. git use your favourite editor to edit commit messages, and if you already have an instance of the editor running, the editing will happen in the running instance, instead of opening a new one. An important aspect of this use case is that the process that gets started by git does not return until the editing is done.

Normally, the commandline is completely handled in the “command-line” handler. The launching instance exits once the signal handler in the primary instance has returned, and the return value of the signal handler becomes the exit status of the launching instance.

static int
command_line (GApplication            *application,
              GApplicationCommandLine *cmdline)
{
  gchar **argv;
  gint argc;
  gint i;

  argv = g_application_command_line_get_arguments (cmdline, &argc);

  g_application_command_line_print (cmdline,
                                    "This text is written back\n"
                                    "to stdout of the caller\n");

  for (i = 0; i < argc; i++)
    g_print ("argument %d: %s\n", i, argv[i]);

  g_strfreev (argv);

  return 0;
}

The complete example can be found here: gapplication-example-cmdline.c

In more complicated cases, the handling of the comandline can be split between the launcher and the primary instance.

static gboolean
 test_local_cmdline (GApplication   *application,
                     gchar        ***arguments,
                     gint           *exit_status)
{
  gint i, j;
  gchar **argv;

  argv = *arguments;

  i = 1;
  while (argv[i])
    {
      if (g_str_has_prefix (argv[i], "--local-"))
        {
          g_print ("handling argument %s locally\n", argv[i]);
          g_free (argv[i]);
          for (j = i; argv[j]; j++)
            argv[j] = argv[j + 1];
        }
      else
        {
          g_print ("not handling argument %s locally\n", argv[i]);
          i++;
        }
    }

  *exit_status = 0;

  return FALSE;
}

static void
test_application_class_init (TestApplicationClass *class)
{
  G_APPLICATION_CLASS (class)->local_command_line = test_local_cmdline;

  ...
}

In this example of split commandline handling, options that start with --local- are handled locally, all other options are passed to the “command-line” handler which runs in the primary instance.

The complete example can be found here: gapplication-example-cmdline2.c

If handling the commandline requires a lot of work, it may be better to defer it.

static gboolean
my_cmdline_handler (gpointer data)
{
  GApplicationCommandLine *cmdline = data;

  // do the heavy lifting in an idle

  g_application_command_line_set_exit_status (cmdline, 0);
  g_object_unref (cmdline); // this releases the application

  return G_SOURCE_REMOVE;
}

static int
command_line (GApplication            *application,
              GApplicationCommandLine *cmdline)
{
  // keep the application running until we are done with this commandline
  g_application_hold (application);

  g_object_set_data_full (G_OBJECT (cmdline),
                          "application", application,
                          (GDestroyNotify)g_application_release);

  g_object_ref (cmdline);
  g_idle_add (my_cmdline_handler, cmdline);

  return 0;
}

In this example the commandline is not completely handled before the “command-line” handler returns. Instead, we keep a reference to the GApplicationCommandLine object and handle it later (in this example, in an idle). Note that it is necessary to hold the application until you are done with the commandline.

The complete example can be found here: gapplication-example-cmdline3.c

Functions

g_application_command_line_get_arguments ()

gchar **
g_application_command_line_get_arguments
                               (GApplicationCommandLine *cmdline,
                                int *argc);

Gets the list of arguments that was passed on the command line.

The strings in the array may contain non-UTF-8 data on UNIX (such as filenames or arguments given in the system locale) but are always in UTF-8 on Windows.

If you wish to use the return value with GOptionContext, you must use g_option_context_parse_strv().

The return value is NULL-terminated and should be freed using g_strfreev().

Parameters

cmdline	a GApplicationCommandLine
argc	the length of the arguments array, or `NULL`.	[out][allow-none]

Returns

the string array containing the arguments (the argv).

[array length=argc][transfer full]

Since 2.28

g_application_command_line_get_cwd ()

const gchar *
g_application_command_line_get_cwd (GApplicationCommandLine *cmdline);

Gets the working directory of the command line invocation. The string may contain non-utf8 data.

It is possible that the remote application did not send a working directory, so this may be NULL.

The return value should not be modified or freed and is valid for as long as cmdline exists.

Parameters

cmdline

a GApplicationCommandLine

Returns

the current directory, or NULL

Since 2.28

g_application_command_line_get_environ ()

const gchar * const *
g_application_command_line_get_environ
                               (GApplicationCommandLine *cmdline);

Gets the contents of the 'environ' variable of the command line invocation, as would be returned by g_get_environ(), ie as a NULL-terminated list of strings in the form 'NAME=VALUE'. The strings may contain non-utf8 data.

The remote application usually does not send an environment. Use G_APPLICATION_SEND_ENVIRONMENT to affect that. Even with this flag set it is possible that the environment is still not available (due to invocation messages from other applications).

The return value should not be modified or freed and is valid for as long as cmdline exists.

See g_application_command_line_getenv() if you are only interested in the value of a single environment variable.

Parameters

cmdline

a GApplicationCommandLine

Returns

the environment strings, or NULL if they were not sent.

[array zero-terminated=1][transfer none]

Since 2.28

g_application_command_line_get_options_dict ()

GVariantDict *
g_application_command_line_get_options_dict
                               (GApplicationCommandLine *cmdline);

Gets the options there were passed to g_application_command_line().

If you did not override local_command_line() then these are the same options that were parsed according to the GOptionEntrys added to the application with g_application_add_main_option_entries() and possibly modified from your GApplication::handle-local-options handler.

If no options were sent then an empty dictionary is returned so that you don't need to check for NULL.

Parameters

cmdline

a GApplicationCommandLine

Returns

a GVariantDict with the options.

[transfer none]

Since 2.40

g_application_command_line_get_stdin ()

GInputStream *
g_application_command_line_get_stdin (GApplicationCommandLine *cmdline);

Gets the stdin of the invoking process.

The GInputStream can be used to read data passed to the standard input of the invoking process. This doesn't work on all platforms. Presently, it is only available on UNIX when using a DBus daemon capable of passing file descriptors. If stdin is not available then NULL will be returned. In the future, support may be expanded to other platforms.

You must only call this function once per commandline invocation.

Parameters

cmdline

a GApplicationCommandLine

Returns

a GInputStream for stdin.

[transfer full]

Since 2.34

g_application_command_line_create_file_for_arg ()

GFile *
g_application_command_line_create_file_for_arg
                               (GApplicationCommandLine *cmdline,
                                const gchar *arg);

Creates a GFile corresponding to a filename that was given as part of the invocation of cmdline .

This differs from g_file_new_for_commandline_arg() in that it resolves relative pathnames using the current working directory of the invoking process rather than the local process.

Parameters

cmdline	a GApplicationCommandLine
arg	an argument from `cmdline`

Returns

a new GFile.

[transfer full]

Since 2.36

g_application_command_line_getenv ()

const gchar *
g_application_command_line_getenv (GApplicationCommandLine *cmdline,
                                   const gchar *name);

Gets the value of a particular environment variable of the command line invocation, as would be returned by g_getenv(). The strings may contain non-utf8 data.

The return value should not be modified or freed and is valid for as long as cmdline exists.

Parameters

cmdline	a GApplicationCommandLine
name	the environment variable to get

Returns

the value of the variable, or NULL if unset or unsent

Since 2.28

g_application_command_line_get_is_remote ()

gboolean
g_application_command_line_get_is_remote
                               (GApplicationCommandLine *cmdline);

Determines if cmdline represents a remote invocation.

Parameters

cmdline

a GApplicationCommandLine

Returns

TRUE if the invocation was remote

Since 2.28

g_application_command_line_get_platform_data ()

GVariant *
g_application_command_line_get_platform_data
                               (GApplicationCommandLine *cmdline);

Gets the platform data associated with the invocation of cmdline .

This is a GVariant dictionary containing information about the context in which the invocation occurred. It typically contains information like the current working directory and the startup notification ID.

For local invocation, it will be NULL.

Parameters

cmdline

GApplicationCommandLine

Returns

the platform data, or NULL.

[nullable]

Since 2.28

g_application_command_line_set_exit_status ()

void
g_application_command_line_set_exit_status
                               (GApplicationCommandLine *cmdline,
                                int exit_status);

Sets the exit status that will be used when the invoking process exits.

The return value of the “command-line” signal is passed to this function when the handler returns. This is the usual way of setting the exit status.

In the event that you want the remote invocation to continue running and want to decide on the exit status in the future, you can use this call. For the case of a remote invocation, the remote process will typically exit when the last reference is dropped on cmdline . The exit status of the remote process will be equal to the last value that was set with this function.

In the case that the commandline invocation is local, the situation is slightly more complicated. If the commandline invocation results in the mainloop running (ie: because the use-count of the application increased to a non-zero value) then the application is considered to have been 'successful' in a certain sense, and the exit status is always zero. If the application use count is zero, though, the exit status of the local GApplicationCommandLine is used.

Parameters

cmdline	a GApplicationCommandLine
exit_status	the exit status

Since 2.28

g_application_command_line_get_exit_status ()

int
g_application_command_line_get_exit_status
                               (GApplicationCommandLine *cmdline);

Gets the exit status of cmdline . See g_application_command_line_set_exit_status() for more information.

Parameters

cmdline

a GApplicationCommandLine

Returns

the exit status

Since 2.28

g_application_command_line_print ()

void
g_application_command_line_print (GApplicationCommandLine *cmdline,
                                  const gchar *format,
                                  ...);

Formats a message and prints it using the stdout print handler in the invoking process.

If cmdline is a local invocation then this is exactly equivalent to g_print(). If cmdline is remote then this is equivalent to calling g_print() in the invoking process.

Parameters

cmdline	a GApplicationCommandLine
format	a printf-style format string
...	arguments, as per `format`

Since 2.28

g_application_command_line_printerr ()

void
g_application_command_line_printerr (GApplicationCommandLine *cmdline,
                                     const gchar *format,
                                     ...);

Formats a message and prints it using the stderr print handler in the invoking process.

If cmdline is a local invocation then this is exactly equivalent to g_printerr(). If cmdline is remote then this is equivalent to calling g_printerr() in the invoking process.

Parameters

cmdline	a GApplicationCommandLine
format	a printf-style format string
...	arguments, as per `format`

Since 2.28

Types and Values