KILL(2) System Calls KILL(2)
kill - send signal to a process
int kill (pid_t pid, int sig);
The kill function sends the signal given by sig to pid, a process or a
group of processes. Signals are software interrupts; they act just
like hardware interrupts and can also be used for basic IPC (inter-pro-
Sig may be one of the signals specified in signal(2) or it may be 0, in
which case error checking is performed but no signal is actually sent.
This can be used to check the validity of pid.
For a process to have permission to send a signal to a process desig-
nated by pid, the real or effective user ID of the receiving process
must match that of the sending process or the user must have appropri-
ate 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.
If pid is greater than zero, sig is sent to the process whose ID is
equal to pid.
If pid is zero, sig is sent to all processes whose group ID is equal to
the process group ID of the sender, and for which the process has per-
mission; this is a variant of killpg(2). If pid is -1, and if the user
has super-user privileges, the signal is sent to all processes exclud-
ing system processes and the process sending the signal. If the user
is not the super user, the signal is sent to all processes with the
same uid as the user excluding 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. This is a variant
Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned and errno is set to indicate the error.
Kill will fail and no signal will be sent if:
EINVAL Sig is not a valid signal number.
ESRCH No process can be found corresponding to that specified
ESRCH The process id was given as 0 but the sending process
does not have a process group.
EPERM The sending process is not the super-user and its effec-
tive 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
Do not attempt to send signals from inside a CDA (Classic Desk Acces-
sory) or interrupt handler.
getpid(2), getpgrp(2), killpg(2), signal(2)
The kill function is expected to conform to IEEE Std 1003.1-1988
GNO 16 January 1997 KILL(2)
Man(1) output converted with