# exit

## NAME



           exit - cause normal process termination
    


## LIBRARY



           Standard C library (_libc_ , _-lc_)
    


## SYNOPSIS



           **#include <stdlib.h>**
    
           **[[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)).
    
           All functions registered with atexit(3) and on_exit(3) are called,
           in the reverse order of their registration.  (It is possible for
           one of these functions to use atexit(3) or on_exit(3) 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(2), or kills itself with a signal),
           then none of the remaining functions is called, and further exit
           processing (in particular, flushing of stdio(3) streams) is
           abandoned.  If a function has been registered multiple times using
           atexit(3) or on_exit(3), then it is called as many times as it was
           registered.
    
           All open stdio(3) streams are flushed and closed.  Files created
           by tmpfile(3) 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).
           ┌──────────────────────────┬───────────────┬─────────────────────┐
           │ **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.
    


## NOTES



           The behavior is undefined if one of the functions registered using
           atexit(3) and on_exit(3) calls either **exit**() or longjmp(3).  Note
           that a call to execve(2) removes registrations created using
           atexit(3) and on_exit(3).
    
           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 _< sysexits.h>_.
    
           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) (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) 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) **PR_SET_PDEATHSIG**
           operation to arrange that it receives a signal if its parent
           terminates.
    


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