diff options
Diffstat (limited to 'ev.pod')
| -rw-r--r-- | ev.pod | 56 |
1 files changed, 55 insertions, 1 deletions
@@ -1456,7 +1456,32 @@ Example: Try to exit cleanly on SIGINT and SIGTERM. =head2 C<ev_child> - watch out for process status changes Child watchers trigger when your process receives a SIGCHLD in response to -some child status changes (most typically when a child of yours dies). +some child status changes (most typically when a child of yours dies). It +is permissible to install a child watcher I<after> the child has been +forked (which implies it might have already exited), as long as the event +loop isn't entered (or is continued from a watcher). + +Only the default event loop is capable of handling signals, and therefore +you can only rgeister child watchers in the default event loop. + +=head3 Process Interaction + +Libev grabs C<SIGCHLD> as soon as the default event loop is +initialised. This is necessary to guarantee proper behaviour even if +the first child watcher is started after the child exits. The occurance +of C<SIGCHLD> is recorded asynchronously, but child reaping is done +synchronously as part of the event loop processing. Libev always reaps all +children, even ones not watched. + +=head3 Overriding the Built-In Processing + +Libev offers no special support for overriding the built-in child +processing, but if your application collides with libev's default child +handler, you can override it easily by installing your own handler for +C<SIGCHLD> after initialising the default loop, and making sure the +default loop never gets destroyed. You are encouraged, however, to use an +event-based approach to child reaping and thus use libev's support for +that, so other libev users can use C<ev_child> watchers freely. =head3 Watcher-Specific Functions and Data Members @@ -1490,6 +1515,35 @@ C<waitpid> and C<sys/wait.h> documentation for details). =back +=head3 Examples + +Example: C<fork()> a new process and install a child handler to wait for +its completion. + + ev_child cw; + + static void + child_cb (EV_P_ struct ev_child *w, int revents) + { + ev_child_stop (EV_A_ w); + printf ("process %d exited with status %x\n", w->rpid, w->rstatus); + } + + pid_t pid = fork (); + + if (pid < 0) + // error + else if (pid == 0) + { + // the forked child executes here + exit (1); + } + else + { + ev_child_init (&cw, child_cb, pid, 0); + ev_child_start (EV_DEFAULT_ &cw); + } + =head2 C<ev_stat> - did the file attributes just change? |