.\" Copyright (c) 1980, 1991 Regents of the University of California.
.\" %sccs.include.redist.man%
.\" @(#)kill.2 6.6 (Berkeley) %G%
.Nd send signal to a process
.Fd #include <sys/signal.h>
.Fn kill "pid_t pid" "int sig"
function sends the signal given by
process or a group of processes.
may be one of the signals specified in
or it may be 0, in which case
error checking is performed but no
This can be used to check the validity of
For a process to have permission to send a signal to a process designated
the real or effective user ID of the receving process must match
that of the sending process or the user must have appropriate privileges
(such as given by a set-user-ID program or the user is the super-user).
A single exception is the signal SIGCONT, which may always be sent
to any descendant of the current process.
.It \&If Fa pid No \&is greater than zero :
is sent to the process whose ID is equal to
.It \&If Fa pid No \&is zero :
is sent to all processes whose group ID is equal
to the process group ID of the sender, and for which the
.It \&If Fa pid No \&is -1 :
If the user has super user privileges,
the signal is sent to all processes excluding
system processes. If the user is not the super user,
the signal is sent to all processes with the same uid as the user
except the process sending the signal.
No error is returned if any process could be signaled.
For compatibility with System V,
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.
Upon successful completion, a value of 0 is returned.
Otherwise, a value of -1 is returned and
is set to indicate the error.
will fail and no signal will be sent if:
is not a valid signal number.
No process can be found corresponding to that specified by
The process id was given as 0
but the sending process does not have a process group.
The sending process is not the super-user and its effective
user id does not match the effective user-id of the receiving process.
When signaling a process group, this error is returned if any members
of the group could not be signaled.
conform to IEEE Std 1003.1-1988