TKILL(2)

NAME
tkill, tgkill - send a signal to a single process

SYNOPSIS
#include <sys/types.h>
#include <linux/unistd.h>
#include <errno.h>

_syscall2(int, tkill, int, tid, int, sig)
          /* Using syscall(2) may be preferable; see intro(2) */

int tkill(int tid, int sig);

_syscall3(int, tgkill, int, tgid, int, tid, int, sig)
          /* Using syscall(2) may be preferable; see intro(2) */

int tgkill(int tgid, int tid, int sig);

DESCRIPTION
The tkill() system call is analogous to kill(2), except when the specified process is part of a thread group (created by specifying the CLONE_THREAD flag in the call to clone). Since all the processes in a thread group have the same PID, they cannot be individually signalled with kill(2). With tkill(), however, one can address each process by its unique TID.

The tgkill() call improves on tkill() by allowing the caller to specify the thread group ID of the thread to be signalled, protecting against TID reuse. If the tgid is specified as -1, tgkill() degenerates into tkill().

These are the raw system call interfaces, meant for internal thread library use.

RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

ERRORS

EINVAL
    An invalid TID or signal was specified.

EPERM
    Permission denied. For the required permissions, see kill(2).

ESRCH
    No process with the specified thread ID (and thread group ID) exists.

VERSIONS
tkill() is supported since Linux 2.4.19 / 2.5.4. tgkill() was added in Linux 2.5.75.

CONFORMING TO
tkill() and tgkill() are Linux specific and should not be used in programs that are intended to be portable.

SEE ALSO
gettid(2), kill(2)