tkill(2) — Linux manual page

tkill(2)                   System Calls Manual                  tkill(2)

NAME

       tkill, tgkill - send a signal to a thread

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <signal.h>           /* Definition of SIG* constants */
       #include <sys/syscall.h>      /* Definition of SYS_* constants */
       #include <unistd.h>

       [[deprecated]] int syscall(SYS_tkill, pid_t tid, int sig);

       #include <signal.h>

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

       Note: glibc provides no wrapper for tkill(), necessitating the
       use of syscall(2).

DESCRIPTION

       tgkill() sends the signal sig to the thread with the thread ID
       tid in the thread group tgid.  (By contrast, kill(2) can be used
       to send a signal only to a process (i.e., thread group) as a
       whole, and the signal will be delivered to an arbitrary thread
       within that process.)

       tkill() is an obsolete predecessor to tgkill().  It allows only
       the target thread ID to be specified, which may result in the
       wrong thread being signaled if a thread terminates and its thread
       ID is recycled.  Avoid using this system call.

       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 to indicate the error.

ERRORS

       EAGAIN The RLIMIT_SIGPENDING resource limit was reached and sig
              is a real-time signal.

       EAGAIN Insufficient kernel memory was available and sig is a
              real-time signal.

       EINVAL An invalid thread ID, thread group ID, 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.

STANDARDS

       Linux.

HISTORY

       tkill()
              Linux 2.4.19 / 2.5.4.

       tgkill()
              Linux 2.5.75, glibc 2.30.

NOTES

       See the description of CLONE_THREAD in clone(2) for an
       explanation of thread groups.

SEE ALSO

       clone(2), gettid(2), kill(2), rt_sigqueueinfo(2)

COLOPHON

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Linux man-pages 6.9.1          2024-05-02                       tkill(2)

Pages that refer to this page: clone(2), gettid(2), kill(2), ptrace(2), rt_sigqueueinfo(2), sigaction(2), syscalls(2), raise(3), nptl(7), signal(7)

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