'\" t .\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk .\" .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" .TH pthread_self 3 2023-03-30 "Linux man-pages 6.04" .SH NAME pthread_self \- obtain ID of the calling thread .SH LIBRARY POSIX threads library .RI ( libpthread ", " \-lpthread ) .SH SYNOPSIS .nf .B #include .PP .B pthread_t pthread_self(void); .fi .SH DESCRIPTION The .BR pthread_self () function returns the ID of the calling thread. This is the same value that is returned in .I *thread in the .BR pthread_create (3) call that created this thread. .SH RETURN VALUE This function always succeeds, returning the calling thread's ID. .SH ERRORS This function always succeeds. .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). .ad l .nh .TS allbox; lbx lb lb l l l. Interface Attribute Value T{ .BR pthread_self () T} Thread safety MT-Safe .TE .hy .ad .sp 1 .SH STANDARDS POSIX.1-2008. .SH HISTORY POSIX.1-2001. .SH NOTES POSIX.1 allows an implementation wide freedom in choosing the type used to represent a thread ID; for example, representation using either an arithmetic type or a structure is permitted. Therefore, variables of type .I pthread_t can't portably be compared using the C equality operator (\fB==\fP); use .BR pthread_equal (3) instead. .PP Thread identifiers should be considered opaque: any attempt to use a thread ID other than in pthreads calls is nonportable and can lead to unspecified results. .PP Thread IDs are guaranteed to be unique only within a process. A thread ID may be reused after a terminated thread has been joined, or a detached thread has terminated. .PP The thread ID returned by .BR pthread_self () is not the same thing as the kernel thread ID returned by a call to .BR gettid (2). .SH SEE ALSO .BR pthread_create (3), .BR pthread_equal (3), .BR pthreads (7)