kill.2

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)kill.2	2.1	3/10/87
.TH kill 2
.SH Name
kill \- send signal to a process
.SH Syntax
.nf
#include <sys/types.h>
#include <signal.h>
.PP 
kill(\fIpid, sig\fP)
.br
pid_t \fIpid\fP;
int \fIsig\fP;
.fi
.SH Description
.NXR "kill system call"
.NXA "kill system call" "pause subroutine"
.NXR "process" "signaling"
The system call
.PN kill
sends the signal \fIsig\fP
to a process specified by the process number
.IR pid .
The
.I sig
can be a signal specified in a
.PN sigvec  
call or it can be 0.  If the
.I sig
is 0, error checking is performed, but a signal
is not sent.  This call can be used to check the validity of
.IR pid .
.PP
The sending and receiving processes must
have the same effective user ID, otherwise
this call is restricted to the superuser with the exception
of the signal SIGCONT.  The signal SIGCONT can always be
sent to a child or grandchild of the current process.
.PP
If the process number is 0,
the signal is sent to all other processes in the
sender's process group.
.PP
If the process number 
is negative but not \-1,
the signal
is sent to all processes whose process-group-id is equal to the 
absolute value of the process number.
.PP
The above two options are variants of 
.PN killpg .
.PP
If the process number is \-1, and the user is the superuser,
the signal is broadcast 
for all processes
except to system processes
and the process sending the signal.
.PP
Processes may send signals to themselves.
.SH Environment
System Five
.br
POSIX
.PP
When your program is compiled in the System V or POSIX environment,
a signal is sent if either the real or effective uid of the sending process
matches the real or saved-set-uid (as described in 
.MS execve 2 
)
of the receiving process. In addition, any process can use a
.IR pid
of \-1, and the signal is sent to all processes subject to these 
permission checks.
.PP
In POSIX mode, the
.I pid
argument is of type 
.I pid_t.
.SH Return Values
Upon successful completion, a value of 0 is returned.
Otherwise, a value of \-1 is returned, and
.PN errno
is set to indicate the error.
.SH Diagnostics
The
.PN kill
system call fails under the following conditions:
.TP 15
[EINVAL]
The \fIsig\fP is not a valid signal number.
.TP 15
[EPERM]
The sending process is not the superuser, and its effective
user ID does not match the effective user ID of the receiving process.
.TP 15
[ESRCH]
No process can be found corresponding to that specified by \fIpid\fP.
.SH See Also
execve(2), getpgrp(2), getpid(2), killpg(2), sigvec(2), pause(3)