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NAME

       tkill, tgkill - send a signal to a thread

SYNOPSIS

       int tkill(int tid, int sig);

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

       Note: There is no glibc wrapper for tkill(); see NOTES.

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 appropriately.

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.

VERSIONS

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

       Library support for tgkill() was added to glibc in version 2.30.

CONFORMING TO

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

NOTES

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

       Glibc does not provide a wrapper for tkill(); call it using syscall(2).  Before  glibc  2.30,  there  was
       also no wrapper function for tgkill().

SEE ALSO

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

COLOPHON

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