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.\" Copyright (c) 2016 The FreeBSD Foundation, Inc.
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.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship
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.Dd May 5, 2020
.Dt THR_SELF 2
.Os
.Sh NAME
.Nm thr_self
.Nd return thread identifier for the calling thread
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/thr.h
.Ft int
.Fn thr_self "long *id"
.Sh DESCRIPTION
The
.Fn thr_self
system call stores the system-wide thread identifier for the current
kernel-scheduled thread in the variable pointed by the argument
.Va id .
.Pp
The thread identifier is an integer in the range from
.Dv PID_MAX + 2
(100001) to
.Dv INT_MAX .
The thread identifier is guaranteed to be unique at any given time,
for each running thread in the system.
After the thread exits, the identifier may be reused.
.Sh RETURN VALUES
If successful,
.Fn thr_self
will return zero, otherwise \-1 is returned, and
.Va errno
is set to indicate the error.
.Sh ERRORS
The
.Fn thr_self
operation may return the following errors:
.Bl -tag -width Er
.It Bq Er EFAULT
The memory pointed to by the
.Fa id
argument is not valid.
.El
.Sh SEE ALSO
.Xr thr_exit 2 ,
.Xr thr_kill 2 ,
.Xr thr_kill2 2 ,
.Xr thr_new 2 ,
.Xr thr_set_name 2 ,
.Xr _umtx_op 2 ,
.Xr pthread_getthreadid_np 3 ,
.Xr pthread_self 3
.Sh STANDARDS
The
.Fn thr_self
system call is non-standard and is used by
.Lb libthr
to implement
.St -p1003.1-2001
.Xr pthread 3
functionality.
.Sh HISTORY
The
.Fn thr_self
system call first appeared in
.Fx 5.2 .