exit.2

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 2 代码 · 共 79 行

.\" SCCSID: @(#)exit.2	2.1	3/10/87
.TH exit 2
.SH Name
_exit \- terminate a process
.SH Syntax
.nf
#include <stdlib.h>
void _exit(\fIstatus\fP)
int \fIstatus\fP;
.fi
.SH Description
.NXR "_exit system call"
.NXR "process" "terminating"
The function,
.PN _exit ,
terminates a calling process with the following consequences:
.IP \(bu 5
All of the file descriptors open in the calling process are closed.
.IP \(bu 5
If the parent process of the calling process is executing a
.PN wait ,
it is notified of the calling process's termination and
the low-order eight bits of \fIstatus\fP are made available to it.
For further information, see
.MS wait 2 .
.IP \(bu 5
The parent process ID of all of the calling process's existing child
processes and zombie processes are also set to 1.   
This means that the initialization process
inherits each of these processes as well.
For further information, see
.MS intro 2 ,
.IP \(bu 5
Each attached shared memory segment is detached
and the value of \fIshm_nattach\fP in the data structure
associated with its shared memory identifier is decremented by 1.
.IP \(bu 5
For each semaphore for which the calling process has set
a semadj value, (see 
.MS semop 2 , 
) that semadj value 
is added to the semval of the specified semaphore.
.IP \(bu 5
If the process has a process, text, or data lock, an
unlock is performed.
.IP \(bu 5
An accounting record is written on the accounting file
if the system's accounting routine is enabled. For more information, see
.MS acct 2 .
.PP 
Calling
.PN _exit
directly circumvents all cleanup.
Most C programs call the library routine
.MS exit 3 ,
which performs cleanup actions in the standard I/O library before
calling 
.PN _exit .
.PP
.SH Environment
.SS POSIX, System V
The 
.PN _exit
function differs from the System V as well as POSIX definition in that even if
the calling process is a process group leader, the SIGHUP 
signal is not sent to each process that has a
process group ID equal to that of the calling process.
.PP
The
.PN _exit
function also differs in that the  
.PN exit
routine is declared as type 
.I int
instead of type 
.I void.
.SH See Also
fork(2), wait(2), exit(3), signal(3).