SYS_KILL(9) Driver Basics SYS_KILL(9)NAME
sys_kill - send a signal to a process
SYNOPSIS
long sys_kill(pid_t pid, int sig);
ARGUMENTS
pid
the PID of the process
sig
signal to be sent
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KILL(2) Linux Programmer's Manual KILL(2)NAME
kill - send signal to a process
SYNOPSIS
#include <sys/types.h>
#include <signal.h>
int kill(pid_t pid, int sig);
DESCRIPTION
The kill system call can be used to send any signal to any process group or process.
If pid is positive, then signal sig is sent to pid.
If pid equals 0, then sig is sent to every process in the process group of the current process.
If pid equals -1, then sig is sent to every process except for process 1 (init), but see below.
If pid is less than -1, then sig is sent to every process in the process group -pid.
If sig is 0, then no signal is sent, but error checking is still performed.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
ERRORS
EINVAL An invalid signal was specified.
ESRCH The pid or process group does not exist. Note that an existing process might be a zombie, a process which already committed termi-
nation, but has not yet been wait()ed for.
EPERM The process does not have permission to send the signal to any of the receiving processes. For a process to have permission to send
a signal to process pid it must either have root privileges, or the real or effective user ID of the sending process must equal the
real or saved set-user-ID of the receiving process. In the case of SIGCONT it suffices when the sending and receiving processes
belong to the same session.
NOTES
It is impossible to send a signal to task number one, the init process, for which it has not installed a signal handler. This is done to
assure the system is not brought down accidentally.
POSIX 1003.1-2001 requires that kill(-1,sig) send sig to all processes that the current process may send signals to, except possibly for
some implementation-defined system processes. Linux allows a process to signal itself, but on Linux the call kill(-1,sig) does not signal
the current process.
LINUX HISTORY
Across different kernel versions, Linux has enforced different rules for the permissions required for an unprivileged process to send a
signal to another process. In kernels 1.0 to 1.2.2, a signal could be sent if the effective user ID of the sender matched that of the
receiver, or the real user ID of the sender matched that of the receiver. From kernel 1.2.3 until 1.3.77, a signal could be sent if the
effective user ID of the sender matched either the real or effective user ID of the receiver. The current rules, which conform to POSIX
1003.1-2001, were adopted in kernel 1.3.78.
CONFORMING TO
SVr4, SVID, POSIX.1, X/OPEN, BSD 4.3, POSIX 1003.1-2001
SEE ALSO _exit(2), exit(3), signal(2), signal(7)Linux 2.5.0 2001-12-18 KILL(2)