_exit.2

早期freebsd实现

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.\"     @(#)_exit.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt EXIT 2
.Os BSD 4
.Sh NAME
.Nm _exit
.Nd terminate the calling process
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft void
.Fn _exit "int status"
.Sh DESCRIPTION
The
.Fn _exit
function
terminates a process with the following consequences:
.Bl -bullet
.It
All of the descriptors open in the calling process are closed.
This may entail delays, for example, waiting for output to drain;
a process in this state may not be killed, as it is already dying.
.It
If the parent process of the calling process has an outstanding
.Xr wait
call
or catches the
.Dv SIGCHLD
signal,
it is notified of the calling process's termination and
the
.Em status
is set as defined by
.Xr wait 2 .
.It
The parent process-ID of all of the calling process's existing child
processes are set to 1; the initialization process
(see the DEFINITIONS section of
.Xr intro 2 )
inherits each of these processes.
.It
If the termination of the process causes any process group
to become orphaned (usually because the parents of all members
of the group have now exited; see
.Dq orphaned process group
in
.Xr intro 2 ) ,
and if any member of the orphaned group is stopped,
the
.Dv SIGHUP
signal and the
.Dv SIGCONT
signal are sent to all members of the newly-orphaned process group.
.It
If the process is a controlling process (see
.Xr intro 2 ) ,
the
.Dv SIGHUP
signal is sent to the foreground process group of the controlling terminal,
and all current access to the controlling terminal is revoked.
.El
.Pp
Most C programs call the library routine
.Xr exit 3 ,
which flushes buffers, closes streams, unlinks temporary files, etc.,
before
calling
.Fn _exit .
.Sh RETURN VALUE
.Fn _exit
can never return.
.Sh SEE ALSO
.Xr fork 2 ,
.Xr sigvec 2 ,
.Xr wait 2 ,
.Xr exit 3
.Sh STANDARDS
The
.Nm _exit
function is defined by
.St -p1003.1-88 .