UNIX-specific utilities and integration

UNIX-specific utilities and integration — pipes, signal handling

Synopsis

#include <glib-unix.h>

#define             G_UNIX_ERROR
gboolean            g_unix_open_pipe                    (gint *fds,
                                                         gint flags,
                                                         GError **error);
gboolean            g_unix_set_fd_nonblocking           (gint fd,
                                                         gboolean nonblock,
                                                         GError **error);

guint               g_unix_signal_add                   (gint signum,
                                                         GSourceFunc handler,
                                                         gpointer user_data);
guint               g_unix_signal_add_full              (gint priority,
                                                         gint signum,
                                                         GSourceFunc handler,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
GSource *           g_unix_signal_source_new            (gint signum);

gboolean            (*GUnixFDSourceFunc)                (gint fd,
                                                         GIOCondition condition,
                                                         gpointer user_data);
guint               g_unix_fd_add                       (gint fd,
                                                         GIOCondition condition,
                                                         GUnixFDSourceFunc function,
                                                         gpointer user_data);
guint               g_unix_fd_add_full                  (gint priority,
                                                         gint fd,
                                                         GIOCondition condition,
                                                         GUnixFDSourceFunc function,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
GSource *           g_unix_fd_source_new                (gint fd,
                                                         GIOCondition condition);

Description

Most of GLib is intended to be portable; in contrast, this set of functions is designed for programs which explicitly target UNIX, or are using it to build higher level abstractions which would be conditionally compiled if the platform matches G_OS_UNIX.

To use these functions, you must explicitly include the "glib-unix.h" header.

Details

G_UNIX_ERROR

#define G_UNIX_ERROR (g_unix_error_quark())

Error domain for API in the "g_unix_" namespace. Note that there is no exported enumeration mapping errno. Instead, all functions ensure that errno is relevant. The code for all G_UNIX_ERROR is always 0, and the error message is always generated via g_strerror().

It is expected that most code will not look at errno from these APIs. Important cases where one would want to differentiate between errors are already covered by existing cross-platform GLib API, such as e.g. GFile wrapping ENOENT. However, it is provided for completeness, at least.


g_unix_open_pipe ()

gboolean            g_unix_open_pipe                    (gint *fds,
                                                         gint flags,
                                                         GError **error);

Similar to the UNIX pipe() call, but on modern systems like Linux uses the pipe2() system call, which atomically creates a pipe with the configured flags. The only supported flag currently is FD_CLOEXEC. If for example you want to configure O_NONBLOCK, that must still be done separately with fcntl().

Note

This function does *not* take O_CLOEXEC, it takes FD_CLOEXEC as if for fcntl(); these are different on Linux/glibc.

fds :

Array of two integers

flags :

Bitfield of file descriptor flags, see "man 2 fcntl"

error :

a GError

Returns :

TRUE on success, FALSE if not (and errno will be set).

Since 2.30


g_unix_set_fd_nonblocking ()

gboolean            g_unix_set_fd_nonblocking           (gint fd,
                                                         gboolean nonblock,
                                                         GError **error);

Control the non-blocking state of the given file descriptor, according to nonblock. On most systems this uses O_NONBLOCK, but on some older ones may use O_NDELAY.

fd :

A file descriptor

nonblock :

If TRUE, set the descriptor to be non-blocking

error :

a GError

Returns :

TRUE if successful

Since 2.30


g_unix_signal_add ()

guint               g_unix_signal_add                   (gint signum,
                                                         GSourceFunc handler,
                                                         gpointer user_data);

A convenience function for g_unix_signal_source_new(), which attaches to the default GMainContext. You can remove the watch using g_source_remove().

signum :

Signal number

handler :

Callback

user_data :

Data for handler

Returns :

An ID (greater than 0) for the event source

Since 2.30


g_unix_signal_add_full ()

guint               g_unix_signal_add_full              (gint priority,
                                                         gint signum,
                                                         GSourceFunc handler,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

A convenience function for g_unix_signal_source_new(), which attaches to the default GMainContext. You can remove the watch using g_source_remove().

priority :

the priority of the signal source. Typically this will be in the range between G_PRIORITY_DEFAULT and G_PRIORITY_HIGH.

signum :

Signal number

handler :

Callback

user_data :

Data for handler

notify :

GDestroyNotify for handler

Returns :

An ID (greater than 0) for the event source Rename to: g_unix_signal_add

Since 2.30


g_unix_signal_source_new ()

GSource *           g_unix_signal_source_new            (gint signum);

Create a GSource that will be dispatched upon delivery of the UNIX signal signum. In GLib versions before 2.36, only SIGHUP, SIGINT, SIGTERM can be monitored. In GLib 2.36, SIGUSR1 and SIGUSR2 were added.

Note that unlike the UNIX default, all sources which have created a watch will be dispatched, regardless of which underlying thread invoked g_unix_signal_source_new().

For example, an effective use of this function is to handle SIGTERM cleanly; flushing any outstanding files, and then calling g_main_loop_quit(). It is not safe to do any of this a regular UNIX signal handler; your handler may be invoked while malloc() or another library function is running, causing reentrancy if you attempt to use it from the handler. None of the GLib/GObject API is safe against this kind of reentrancy.

The interaction of this source when combined with native UNIX functions like sigprocmask() is not defined.

The source will not initially be associated with any GMainContext and must be added to one with g_source_attach() before it will be executed.

signum :

A signal number

Returns :

A newly created GSource

Since 2.30


GUnixFDSourceFunc ()

gboolean            (*GUnixFDSourceFunc)                (gint fd,
                                                         GIOCondition condition,
                                                         gpointer user_data);

The type of functions to be called when a UNIX fd watch source triggers.

fd :

the fd that triggered the event

condition :

the IO conditions reported on fd

user_data :

user data passed to g_unix_fd_add()

Returns :

FALSE if the source should be removed

g_unix_fd_add ()

guint               g_unix_fd_add                       (gint fd,
                                                         GIOCondition condition,
                                                         GUnixFDSourceFunc function,
                                                         gpointer user_data);

Sets a function to be called when the IO condition, as specified by condition becomes true for fd.

function will be called when the specified IO condition becomes TRUE. The function is expected to clear whatever event caused the IO condition to become true and return TRUE in order to be notified when it happens again. If function returns FALSE then the watch will be cancelled.

The return value of this function can be passed to g_source_remove() to cancel the watch at any time that it exists.

The source will never close the fd -- you must do it yourself.

fd :

a file descriptor

condition :

IO conditions to watch for on fd

function :

a GPollFDFunc

user_data :

data to pass to function

Returns :

the ID (greater than 0) of the event source

Since 2.36


g_unix_fd_add_full ()

guint               g_unix_fd_add_full                  (gint priority,
                                                         gint fd,
                                                         GIOCondition condition,
                                                         GUnixFDSourceFunc function,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Sets a function to be called when the IO condition, as specified by condition becomes true for fd.

This is the same as g_unix_fd_add(), except that it allows you to specify a non-default priority and a provide a GDestroyNotify for user_data.

priority :

the priority of the source

fd :

a file descriptor

condition :

IO conditions to watch for on fd

function :

a GUnixFDSourceFunc

user_data :

data to pass to function

notify :

function to call when the idle is removed, or NULL

Returns :

the ID (greater than 0) of the event source

Since 2.36


g_unix_fd_source_new ()

GSource *           g_unix_fd_source_new                (gint fd,
                                                         GIOCondition condition);

Creates a GSource to watch for a particular IO condition on a file descriptor.

The source will never close the fd -- you must do it yourself.

fd :

a file descriptor

condition :

IO conditions to watch for on fd

Returns :

the newly created GSource

Since 2.36