man-pages/man3/pthread_setname_np.3

.\" Copyright (C) 2012 Chandan Apsangi <chandan.jc@gmail.com>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.TH PTHREAD_SETNAME_NP 3 2012-10-24 "Linux" "Linux Programmer's Manual"
.SH NAME
pthread_setname_np, pthread_getname_np \- set/get the name of a thread
.SH SYNOPSIS
.nf
.BR "#define _GNU_SOURCE" "             /* See feature_test_macros(7) */"
.B #include <pthread.h>
.BI "int pthread_setname_np(pthread_t *" thread ", const char *" name ");
.BI "int pthread_getname_np(pthread_t *" thread ", const char *" name
", size_t" len);
.fi
.sp
Compile and link with \fI\-pthread\fP.
.SH DESCRIPTION
By default, all the threads created using
.BR pthread_create (3)
inherit the program name.
Using
.BR pthread_setname_np (3),
users can specify a unique name for a thread,
which can be particularly useful for debugging complicated
multi-threaded applications.
The thread name is a meaningful C language string, whose length is
restricted to 16 characters.
Anything greater than this would lead to an error.

The
.BR pthread_getname_np (3)
can be used to retrieve the name of the thread.
The buffer specified by name must be at least 16 characters in length.
The returned thread name in the output buffer will be null terminated.
.SH RETURN VALUE
On success, these functions return 0;
on error, they return a nonzero error number.
.SH ERRORS
If the functions fail to open /proc/self/task/<TID>/comm, then the
call may fail with one of
the errors described in
.BR open (2).
.TP
.B ERANGE
The length of the string specified as second argument exceeds the allowed limit.

.SH NOTES
.BR pthread_setname_np (3)
internally writes to the thread specific comm file under
.IR /proc
filesystem:
.IR /proc/self/task/<tid>/comm.
.BR pthread_getname_np (3)
retreives it from the same location.

.SH EXAMPLE
.PP
The program below demonstrates the use of
.BR pthread_setname_np (),
as well as
.BR pthread_getname_np ().

The following shell session shows a sample run of the program:
.in +4n
.nf

.RB "$" " ./a.out 1 2 4 7 14"
Created a thread. Default name is: a.out
The thread name after setting it is THREADFOO.
Done
.fi
.in

.SS Program source
\&
.nf
#define _GNU_SOURCE

#include <pthread.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>

#define NAMELEN 16

#define errExitEN(en, msg) \\
        do { if(en) { errno = en; perror(msg); \\
                exit(EXIT_FAILURE);} \\
        } while (0)

static void *threadfunc(void *parm)
{
    sleep(5);                   // allow main program to set the thread name
    return NULL;
}

int main(int argc, char **argv)
{
    pthread_t thread;
    int rc;
    char thread_name[NAMELEN];

    rc = pthread_create(&thread, NULL, threadfunc, NULL);
    errExitEN(rc, "pthread_create");
    rc = pthread_getname_np(thread, thread_name, NAMELEN);
    errExitEN(rc, "pthread_getname_np");
    printf("Created a thread. Default name is: %s\\n", thread_name);
    rc = pthread_setname_np(thread, "THREADFOO");
    errExitEN(rc, "pthread_setname_np");
    sleep(2);
    rc = pthread_getname_np(thread, thread_name, NAMELEN);
    errExitEN(rc, "pthread_getname_np");
    printf("The thread name after setting it is %s.\\n", thread_name);
    rc = pthread_join(thread, NULL);
    errExitEN(rc, "pthread_join");
    printf("Done\\n");
    exit(EXIT_SUCCESS);
}
.fi
.SH SEE ALSO
.ad l
.nh
.BR prctl (2),
.BR pthread_create (3),
.BR pthreads (7)