since: 2.4


g_child_watch_source_new (
  GPid pid


Creates a new child_watch source.

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.

Note that child watch sources can only be used in conjunction with g_spawn... when the G_SPAWN_DO_NOT_REAP_CHILD flag is used.

Note that on platforms where GPid must be explicitly closed (see g_spawn_close_pid()) pid must not be closed while the source is still active. Typically, you will want to call g_spawn_close_pid() in the callback function for the source.

On POSIX platforms, the following restrictions apply to this API due to limitations in POSIX process interfaces:

  • pid must be a child of this process
  • pid must be positive
  • the application must not call waitpid with a non-positive first argument, for instance in another thread
  • the application must not wait for pid to exit by any other mechanism, including waitpid(pid, ...) or a second child-watch source for the same pid
  • the application must not ignore SIGCHLD

If any of those conditions are not met, this and related APIs will not work correctly. This can often be diagnosed via a GLib warning stating that ECHILD was received by waitpid.

Calling waitpid for specific processes other than pid remains a valid thing to do.

Available since: 2.4



Type: GPid

Process to watch. On POSIX the positive pid of a child process. On Windows a handle for a process (which doesn’t have to be a child).

Return value

Type: GSource

The newly-created child watch source.

The caller of the function takes ownership of the data, and is responsible for freeing it.