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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |ATTRIBUTES |STANDARDS |HISTORY |NOTES |EXAMPLES |SEE ALSO |COLOPHON | |
pthread_attr_init(3) Library Functions Manualpthread_attr_init(3)pthread_attr_init, pthread_attr_destroy - initialize and destroy thread attributes object
POSIX threads library (libpthread,-lpthread)
#include <pthread.h>int pthread_attr_init(pthread_attr_t *attr);int pthread_attr_destroy(pthread_attr_t *attr);
Thepthread_attr_init() function initializes the thread attributes object pointed to byattr with default attribute values. After this call, individual attributes of the object can be set using various related functions (listed under SEE ALSO), and then the object can be used in one or morepthread_create(3) calls that create threads. Callingpthread_attr_init() on a thread attributes object that has already been initialized results in undefined behavior. When a thread attributes object is no longer required, it should be destroyed using thepthread_attr_destroy() function. Destroying a thread attributes object has no effect on threads that were created using that object. Once a thread attributes object has been destroyed, it can be reinitialized usingpthread_attr_init(). Any other use of a destroyed thread attributes object has undefined results.
On success, these functions return 0; on error, they return a nonzero error number.
POSIX.1 documents anENOMEMerror forpthread_attr_init(); on Linux these functions always succeed (but portable and future- proof applications should nevertheless handle a possible error return).
For an explanation of the terms used in this section, seeattributes(7). ┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface│Attribute│Value│ ├──────────────────────────────────────┼───────────────┼─────────┤ │pthread_attr_init(), │ Thread safety │ MT-Safe │ │pthread_attr_destroy() │ │ │ └──────────────────────────────────────┴───────────────┴─────────┘
POSIX.1-2008.
POSIX.1-2001.
Thepthread_attr_t type should be treated as opaque: any access to the object other than via pthreads functions is nonportable and produces undefined results.
The program below optionally makes use ofpthread_attr_init() and various related functions to initialize a thread attributes object that is used to create a single thread. Once created, the thread uses thepthread_getattr_np(3) function (a nonstandard GNU extension) to retrieve the thread's attributes, and then displays those attributes. If the program is run with no command-line argument, then it passes NULL as theattr argument ofpthread_create(3), so that the thread is created with default attributes. Running the program on Linux/x86-32 with the NPTL threading implementation, we see the following: $ulimit -s# No stack limit ==> default stack size is 2 MB unlimited $./a.out Thread attributes: Detach state = PTHREAD_CREATE_JOINABLE Scope = PTHREAD_SCOPE_SYSTEM Inherit scheduler = PTHREAD_INHERIT_SCHED Scheduling policy = SCHED_OTHER Scheduling priority = 0 Guard size = 4096 bytes Stack address = 0x40196000 Stack size = 0x201000 bytes When we supply a stack size as a command-line argument, the program initializes a thread attributes object, sets various attributes in that object, and passes a pointer to the object in the call topthread_create(3). Running the program on Linux/x86-32 with the NPTL threading implementation, we see the following: $./a.out 0x3000000 posix_memalign() allocated at 0x40197000 Thread attributes: Detach state = PTHREAD_CREATE_DETACHED Scope = PTHREAD_SCOPE_SYSTEM Inherit scheduler = PTHREAD_EXPLICIT_SCHED Scheduling policy = SCHED_OTHER Scheduling priority = 0 Guard size = 0 bytes Stack address = 0x40197000 Stack size = 0x3000000 bytesProgram source #define _GNU_SOURCE /* To get pthread_getattr_np() declaration */ #include <err.h> #include <errno.h> #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> static void display_pthread_attr(pthread_attr_t *attr, char *prefix) { int s, i; size_t v; void *stkaddr; struct sched_param sp; s = pthread_attr_getdetachstate(attr, &i); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_getdetachstate"); printf("%sDetach state = %s\n", prefix, (i == PTHREAD_CREATE_DETACHED) ? "PTHREAD_CREATE_DETACHED" : (i == PTHREAD_CREATE_JOINABLE) ? "PTHREAD_CREATE_JOINABLE" : "???"); s = pthread_attr_getscope(attr, &i); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_getscope"); printf("%sScope = %s\n", prefix, (i == PTHREAD_SCOPE_SYSTEM) ? "PTHREAD_SCOPE_SYSTEM" : (i == PTHREAD_SCOPE_PROCESS) ? "PTHREAD_SCOPE_PROCESS" : "???"); s = pthread_attr_getinheritsched(attr, &i); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_getinheritsched"); printf("%sInherit scheduler = %s\n", prefix, (i == PTHREAD_INHERIT_SCHED) ? "PTHREAD_INHERIT_SCHED" : (i == PTHREAD_EXPLICIT_SCHED) ? "PTHREAD_EXPLICIT_SCHED" : "???"); s = pthread_attr_getschedpolicy(attr, &i); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_getschedpolicy"); printf("%sScheduling policy = %s\n", prefix, (i == SCHED_OTHER) ? "SCHED_OTHER" : (i == SCHED_FIFO) ? "SCHED_FIFO" : (i == SCHED_RR) ? "SCHED_RR" : "???"); s = pthread_attr_getschedparam(attr, &sp); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_getschedparam"); printf("%sScheduling priority = %d\n", prefix, sp.sched_priority); s = pthread_attr_getguardsize(attr, &v); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_getguardsize"); printf("%sGuard size = %zu bytes\n", prefix, v); s = pthread_attr_getstack(attr, &stkaddr, &v); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_getstack"); printf("%sStack address = %p\n", prefix, stkaddr); printf("%sStack size = %#zx bytes\n", prefix, v); } static void * thread_start(void *arg) { int s; pthread_attr_t gattr; /* pthread_getattr_np() is a non-standard GNU extension that retrieves the attributes of the thread specified in its first argument. */ s = pthread_getattr_np(pthread_self(), &gattr); if (s != 0) errc(EXIT_FAILURE, s, "pthread_getattr_np"); printf("Thread attributes:\n"); display_pthread_attr(&gattr, "\t"); exit(EXIT_SUCCESS); /* Terminate all threads */ } int main(int argc, char *argv[]) { pthread_t thr; pthread_attr_t attr; pthread_attr_t *attrp; /* NULL or &attr */ int s; attrp = NULL; /* If a command-line argument was supplied, use it to set the stack-size attribute and set a few other thread attributes, and set attrp pointing to thread attributes object. */ if (argc > 1) { size_t stack_size; void *sp; attrp = &attr; s = pthread_attr_init(&attr); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_init"); s = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_setdetachstate"); s = pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_setinheritsched"); stack_size = strtoul(argv[1], NULL, 0); s = posix_memalign(&sp, sysconf(_SC_PAGESIZE), stack_size); if (s != 0) errc(EXIT_FAILURE, s, "posix_memalign"); printf("posix_memalign() allocated at %p\n", sp); s = pthread_attr_setstack(&attr, sp, stack_size); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_setstack"); } s = pthread_create(&thr, attrp, &thread_start, NULL); if (s != 0) errc(EXIT_FAILURE, s, "pthread_create"); if (attrp != NULL) { s = pthread_attr_destroy(attrp); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_destroy"); } pause(); /* Terminates when other thread calls exit() */ }pthread_attr_setaffinity_np(3),pthread_attr_setdetachstate(3),pthread_attr_setguardsize(3),pthread_attr_setinheritsched(3),pthread_attr_setschedparam(3),pthread_attr_setschedpolicy(3),pthread_attr_setscope(3),pthread_attr_setsigmask_np(3),pthread_attr_setstack(3),pthread_attr_setstackaddr(3),pthread_attr_setstacksize(3),pthread_create(3),pthread_getattr_np(3),pthread_setattr_default_np(3),pthreads(7)
This page is part of theman-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17pthread_attr_init(3)Pages that refer to this page:pthread_attr_setaffinity_np(3), pthread_attr_setdetachstate(3), pthread_attr_setguardsize(3), pthread_attr_setinheritsched(3), pthread_attr_setschedparam(3), pthread_attr_setschedpolicy(3), pthread_attr_setscope(3), pthread_attr_setsigmask_np(3), pthread_attr_setstack(3), pthread_attr_setstackaddr(3), pthread_attr_setstacksize(3), pthread_create(3), pthread_getattr_default_np(3), pthread_getattr_np(3), pthread_setschedparam(3), pthread_setschedprio(3), sigevent(3type), pthreads(7)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |