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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |ATTRIBUTES |STANDARDS |HISTORY |EXAMPLES |SEE ALSO |COLOPHON | |
pthread_getattr_np(3) Library Functions Manualpthread_getattr_np(3)pthread_getattr_np - get attributes of created thread
POSIX threads library (libpthread,-lpthread)
#define _GNU_SOURCE/* See feature_test_macros(7) */#include <pthread.h>int pthread_getattr_np(pthread_tthread, pthread_attr_t *attr);
Thepthread_getattr_np() function initializes the thread attributes object referred to byattr so that it contains actual attribute values describing the running threadthread. The returned attribute values may differ from the corresponding attribute values passed in theattr object that was used to create the thread usingpthread_create(3). In particular, the following attributes may differ: • the detach state, since a joinable thread may have detached itself after creation; • the stack size, which the implementation may align to a suitable boundary. • and the guard size, which the implementation may round upward to a multiple of the page size, or ignore (i.e., treat as 0), if the application is allocating its own stack. Furthermore, if the stack address attribute was not set in the thread attributes object used to create the thread, then the returned thread attributes object will report the actual stack address that the implementation selected for the thread. When the thread attributes object returned bypthread_getattr_np() is no longer required, it should be destroyed usingpthread_attr_destroy(3).
On success, this function returns 0; on error, it returns a nonzero error number.
ENOMEMInsufficient memory. In addition, ifthread refers to the main thread, thenpthread_getattr_np() can fail because of errors from various underlying calls:fopen(3), if/proc/self/maps can't be opened; andgetrlimit(2), if theRLIMIT_STACKresource limit is not supported.
For an explanation of the terms used in this section, seeattributes(7). ┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface│Attribute│Value│ ├──────────────────────────────────────┼───────────────┼─────────┤ │pthread_getattr_np() │ Thread safety │ MT-Safe │ └──────────────────────────────────────┴───────────────┴─────────┘
GNU; hence the suffix "_np" (nonportable) in the name.
glibc 2.2.3.
The program below demonstrates the use ofpthread_getattr_np(). The program creates a thread that then usespthread_getattr_np() to retrieve and display its guard size, stack address, and stack size attributes. Command-line arguments can be used to set these attributes to values other than the default when creating the thread. The shell sessions below demonstrate the use of the program. In the first run, on an x86-32 system, a thread is created using default attributes: $ulimit -s# No stack limit ==> default stack size is 2 MB unlimited $./a.out Attributes of created thread: Guard size = 4096 bytes Stack address = 0x40196000 (EOS = 0x40397000) Stack size = 0x201000 (2101248) bytes In the following run, we see that if a guard size is specified, it is rounded up to the next multiple of the system page size (4096 bytes on x86-32): $./a.out -g 4097 Thread attributes object after initializations: Guard size = 4097 bytes Stack address = (nil) Stack size = 0x0 (0) bytes Attributes of created thread: Guard size = 8192 bytes Stack address = 0x40196000 (EOS = 0x40397000) Stack size = 0x201000 (2101248) bytes In the last run, the program manually allocates a stack for the thread. In this case, the guard size attribute is ignored. $./a.out -g 4096 -s 0x8000 -a Allocated thread stack at 0x804d000 Thread attributes object after initializations: Guard size = 4096 bytes Stack address = 0x804d000 (EOS = 0x8055000) Stack size = 0x8000 (32768) bytes Attributes of created thread: Guard size = 0 bytes Stack address = 0x804d000 (EOS = 0x8055000) Stack size = 0x8000 (32768) 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_stack_related_attributes(pthread_attr_t *attr, char *prefix) { int s; size_t stack_size, guard_size; void *stack_addr; s = pthread_attr_getguardsize(attr, &guard_size); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_getguardsize"); printf("%sGuard size = %zu bytes\n", prefix, guard_size); s = pthread_attr_getstack(attr, &stack_addr, &stack_size); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_getstack"); printf("%sStack address = %p", prefix, stack_addr); if (stack_size > 0) printf(" (EOS = %p)", (char *) stack_addr + stack_size); printf("\n"); printf("%sStack size = %#zx (%zu) bytes\n", prefix, stack_size, stack_size); } static void display_thread_attributes(pthread_t thread, char *prefix) { int s; pthread_attr_t attr; s = pthread_getattr_np(thread, &attr); if (s != 0) errc(EXIT_FAILURE, s, "pthread_getattr_np"); display_stack_related_attributes(&attr, prefix); s = pthread_attr_destroy(&attr); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_destroy"); } static void * /* Start function for thread we create */ thread_start(void *arg) { printf("Attributes of created thread:\n"); display_thread_attributes(pthread_self(), "\t"); exit(EXIT_SUCCESS); /* Terminate all threads */ } static void usage(char *pname, char *msg) { if (msg != NULL) fputs(msg, stderr); fprintf(stderr, "Usage: %s [-s stack-size [-a]]" " [-g guard-size]\n", pname); fprintf(stderr, "\t\t-a means program should allocate stack\n"); exit(EXIT_FAILURE); } static pthread_attr_t * /* Get thread attributes from command line */ get_thread_attributes_from_cl(int argc, char *argv[], pthread_attr_t *attrp) { int s, opt, allocate_stack; size_t stack_size, guard_size; void *stack_addr; pthread_attr_t *ret_attrp = NULL; /* Set to attrp if we initialize a thread attributes object */ allocate_stack = 0; stack_size = -1; guard_size = -1; while ((opt = getopt(argc, argv, "ag:s:")) != -1) { switch (opt) { case 'a': allocate_stack = 1; break; case 'g': guard_size = strtoul(optarg, NULL, 0); break; case 's': stack_size = strtoul(optarg, NULL, 0); break; default: usage(argv[0], NULL); } } if (allocate_stack && stack_size == -1) usage(argv[0], "Specifying -a without -s makes no sense\n"); if (argc > optind) usage(argv[0], "Extraneous command-line arguments\n"); if (stack_size != -1 || guard_size > 0) { ret_attrp = attrp; s = pthread_attr_init(attrp); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_init"); } if (stack_size != -1) { if (!allocate_stack) { s = pthread_attr_setstacksize(attrp, stack_size); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_setstacksize"); } else { s = posix_memalign(&stack_addr, sysconf(_SC_PAGESIZE), stack_size); if (s != 0) errc(EXIT_FAILURE, s, "posix_memalign"); printf("Allocated thread stack at %p\n\n", stack_addr); s = pthread_attr_setstack(attrp, stack_addr, stack_size); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_setstacksize"); } } if (guard_size != -1) { s = pthread_attr_setguardsize(attrp, guard_size); if (s != 0) errc(EXIT_FAILURE, s, "pthread_attr_setstacksize"); } return ret_attrp; } int main(int argc, char *argv[]) { int s; pthread_t thr; pthread_attr_t attr; pthread_attr_t *attrp = NULL; /* Set to &attr if we initialize a thread attributes object */ attrp = get_thread_attributes_from_cl(argc, argv, &attr); if (attrp != NULL) { printf("Thread attributes object after initializations:\n"); display_stack_related_attributes(attrp, "\t"); printf("\n"); } 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_getaffinity_np(3),pthread_attr_getdetachstate(3),pthread_attr_getguardsize(3),pthread_attr_getinheritsched(3),pthread_attr_getschedparam(3),pthread_attr_getschedpolicy(3),pthread_attr_getscope(3),pthread_attr_getstack(3),pthread_attr_getstackaddr(3),pthread_attr_getstacksize(3),pthread_attr_init(3),pthread_create(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_getattr_np(3)Pages that refer to this page:pthread_attr_init(3), pthread_attr_setguardsize(3), pthread_create(3)
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. | |