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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);

DESCRIPTION

       tgkill()  sends  the signal sig to the thread with the thread ID tid in
       the thread group tgid.  (By contrast, kill(2) can only be used to  send
       a  signal  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  only  allows  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.

       If tgid is specified as -1, tgkill() is equivalent to 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.

NOTES

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

       Glibc does not provide wrappers for these system calls; call them using
       syscall(2).

SEE ALSO

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

COLOPHON

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