SysIII/usr/src/man/man2/kill.2

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.TH KILL 2 
.SH NAME
kill \- send a signal to a process or a group of processes
.SH SYNOPSIS
.B int kill (pid, sig)
.br
.B int pid, sig;
.SH DESCRIPTION
.I Kill\^
sends a signal
to a process or a group of processes.
The process or group of
processes to which the signal is to be sent is specified by
.IR pid .
The signal that is to be sent is specified by
.I sig\^
and is either one from the list given in
.IR signal (2),
or 0.
If
.I sig\^
is 0 (the null signal), error checking is performed but no signal is
actually sent.
This can be used to check the validity of
.IR pid .
.PP
The effective user
.SM ID
of the sending process must match the real user
.SM ID
of the receiving process unless, the effective user
.SM ID
of the sending process is super-user, or the process is sending to itself.
.PP
The processes with a process
.SM ID
of 0 and a process
.SM ID
of 1 are special processes (see
.IR intro (2))
and will be referred to below as
.IR proc0 " and " proc1
respectively.
.PP
If
.I pid\^
is greater than zero,
.I sig\^
will be sent to the process whose process
.SM ID
is equal to 
.IR pid .
.I Pid\^
may equal 1.
.PP
If
.I pid\^
is 0,
.I sig\^
will be sent to all processes excluding
.IR proc0 " and " proc1
whose process group
.SM ID
is equal to the process group
.SM ID
of the sender.
.PP
If
.I pid\^
is \-1 and the effective user
.SM ID
of the sender is not super-user,
.I sig\^
will be sent to all processes excluding
.IR proc0 " and " proc1 
whose real user
.SM ID
is equal to the effective user
.SM ID
of the sender.
.PP
If
.I pid\^
is \-1 and the effective user
.SM ID
of the sender is super-user,
.I sig\^
will be sent to all processes excluding
.IR proc0 " and " proc1.
.PP
If
.I pid\^
is negative but not \-1,
.I sig\^
will be sent to all processes whose process group
.SM ID
is equal to the absolute value of
.IR pid .
.PP
.I Kill\^
will fail and no signal will be sent if one or more of the following are true:
.IP
.I Sig\^
is not a valid signal number.
.SM
\%[EINVAL]
.IP
No process can be found corresponding to that specified by
.IR pid .
.SM
\%[ESRCH]
.IP
The sending process is not sending to itself, its effective user
.SM ID
is not super-user, and its effective user
.SM ID
does not match the real user
.SM ID
of the receiving process.
.SM
\%[EPERM]
.SH RETURN VALUE
Upon successful completion, a value of 0 is returned.
Otherwise, a value of \-1 is returned and
.I errno\^
is set to indicate the error.
.SH SEE ALSO
kill(1), getpid(2), setpgrp(2), signal(2).