Editing Child process (section)

==End of life==
When a child process terminates, some information is returned to the parent process.

When a child process terminates before the parent has called [[wait (system call)|wait]], the kernel retains some information about the process, such as its [[exit status]], to enable its parent to call ''wait'' later.<ref name="man2wait">{{man|2|wait|Linux|wait for process to change state}}</ref>  Because the child is still consuming system resources but not executing it is known as a [[zombie process]]. The ''wait'' system call is commonly invoked in the SIGCHLD handler.

[[POSIX.1-2001]] allows a parent process to elect for the kernel to automatically reap child processes that terminate by explicitly setting the disposition of SIGCHLD to SIG_IGN (although ignore is the default, automatic reaping only occurs if the disposition is set to ignore explicitly<ref>{{cite web|url=http://www.win.tue.nl/~aeb/linux/lk/lk-5.html#ss5.5 |title=The Linux kernel: Signals |publisher=Win.tue.nl |date= |accessdate=2014-04-30}}</ref>), or by setting the SA_NOCLDWAIT flag for the SIGCHLD signal.  Linux 2.6 kernels adhere to this behavior, and FreeBSD supports both of these methods since version 5.0.<ref>[http://fuse4bsd.creo.hu/localcgi/man-cgi.cgi?signal+3] {{webarchive|url=https://web.archive.org/web/20110929182629/http://fuse4bsd.creo.hu/localcgi/man-cgi.cgi?signal+3|date=September 29, 2011}}</ref>  However, because of historical differences between [[System V]] and [[BSD]] behaviors with regard to ignoring SIGCHLD, calling ''wait'' remains the most portable paradigm for cleaning up after forked child processes.<ref>{{man|2|sigaction|Linux|examine and change a signal action}}</ref>