--- name: "exit" section: "3" platform: "linux" package: "man-pages" version: "6.19-1" release: "Arch Linux 2026-11-01" platforms: ["linux", "freebsd", "macos"] url: "https://new.carta.tech/exit/3" --- # exit(3) cause normal process termination ## NAME exit - cause normal process termination ## LIBRARY Standard C library (*libc*, *-lc*) ## SYNOPSIS ``` #include ``` **\[\[noreturn\]\] void exit(int** *status***);** ## DESCRIPTION The **exit**() function causes normal process termination and the least significant byte of *status* (i.e., *status & 0xFF*) is returned to the parent (see [**wait**(2)](/wait/2.md)). All functions registered with [**atexit**(3)](/atexit/3.md) and [**on\_exit**(3)](/on_exit/3.md) are called, in the reverse order of their registration. (It is possible for one of these functions to use [**atexit**(3)](/atexit/3.md) or [**on\_exit**(3)](/on_exit/3.md) to register an additional function to be executed during exit processing; the new registration is added to the front of the list of functions that remain to be called.) If one of these functions does not return (e.g., it calls [**\_exit**(3)](/_exit/3.md), or kills itself with a signal), then none of the remaining functions is called, and further exit processing (in particular, flushing of [**stdio**(3)](/stdio/3.md) streams) is abandoned. If a function has been registered multiple times using [**atexit**(3)](/atexit/3.md) or [**on\_exit**(3)](/on_exit/3.md), then it is called as many times as it was registered. All open [**stdio**(3)](/stdio/3.md) streams are flushed and closed. Files created by [**tmpfile**(3)](/tmpfile/3.md) are removed. The C standard specifies two constants, **EXIT\_SUCCESS** and **EXIT\_FAILURE**, that may be passed to **exit**() to indicate successful or unsuccessful termination, respectively. ## RETURN VALUE The **exit**() function does not return. ## ATTRIBUTES For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md). | | | | | --- | --- | --- | | **Interface** | **Attribute** | **Value** | | **exit**() | Thread safety | MT-Unsafe race:exit | The **exit**() function uses a global variable that is not protected, so it is not thread-safe. ## STANDARDS C11, POSIX.1-2008. ## HISTORY C89, POSIX.1-2001, SVr4, 4.3BSD. ## NOTES The behavior is undefined if one of the functions registered using [**atexit**(3)](/atexit/3.md) and [**on\_exit**(3)](/on_exit/3.md) calls either **exit**() or [**longjmp**(3)](/longjmp/3.md). Note that a call to [**execve**(2)](/execve/2.md) removes registrations created using [**atexit**(3)](/atexit/3.md) and [**on\_exit**(3)](/on_exit/3.md). The use of **EXIT\_SUCCESS** and **EXIT\_FAILURE** is slightly more portable (to non-UNIX environments) than the use of 0 and some nonzero value like 1 or -1. In particular, VMS uses a different convention. BSD has attempted to standardize exit codes (which some C libraries such as the GNU C library have also adopted); see the file *\*. After **exit**(), the exit status must be transmitted to the parent process. There are three cases: - • If the parent has set **SA\_NOCLDWAIT**, or has set the **SIGCHLD** handler to **SIG\_IGN**, the status is discarded and the child dies immediately. - • If the parent was waiting on the child, it is notified of the exit status and the child dies immediately. - • Otherwise, the child becomes a "zombie" process: most of the process resources are recycled, but a slot containing minimal information about the child process (termination status, resource usage statistics) is retained in process table. This allows the parent to subsequently use [**waitpid**(2)](/waitpid/2.md) (or similar) to learn the termination status of the child; at that point the zombie process slot is released. If the implementation supports the **SIGCHLD** signal, this signal is sent to the parent. If the parent has set **SA\_NOCLDWAIT**, it is undefined whether a **SIGCHLD** signal is sent. ### Signals sent to other processes If the exiting process is a session leader and its controlling terminal is the controlling terminal of the session, then each process in the foreground process group of this controlling terminal is sent a **SIGHUP** signal, and the terminal is disassociated from this session, allowing it to be acquired by a new controlling process. If the exit of the process causes a process group to become orphaned, and if any member of the newly orphaned process group is stopped, then a **SIGHUP** signal followed by a **SIGCONT** signal will be sent to each process in this process group. See [**setpgid**(2)](/setpgid/2.md) for an explanation of orphaned process groups. Except in the above cases, where the signalled processes may be children of the terminating process, termination of a process does *not* in general cause a signal to be sent to children of that process. However, a process can use the [**prctl**(2)](/prctl/2.md) **PR\_SET\_PDEATHSIG** operation to arrange that it receives a signal if its parent terminates. ## SEE ALSO [**get\_robust\_list**(2)](/get_robust_list/2.md), [**exit**(2)](/exit/2.md), [**setpgid**(2)](/setpgid/2.md), [**wait**(2)](/wait/2.md), [**\_exit**(3)](/_exit/3.md), [**atexit**(3)](/atexit/3.md), [**on\_exit**(3)](/on_exit/3.md), [**tmpfile**(3)](/tmpfile/3.md)