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initgroups(3) — Linux manual page

initgroups(3)            Library Functions Manualinitgroups(3)

NAME        top

       initgroups - initialize the supplementary group access list

LIBRARY        top

       Standard C library (libc,-lc)

SYNOPSIS        top

#include <sys/types.h>#include <grp.h>int initgroups(const char *user, gid_tgroup);   Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):initgroups():           Since glibc 2.19:               _DEFAULT_SOURCE           glibc 2.19 and earlier:               _BSD_SOURCE

DESCRIPTION        top

       Theinitgroups() function initializes the group access list by       reading the group database/etc/group and using all groups of       whichuser is a member.  The additional groupgroup is also added       to the list.       Theuser argument must be non-NULL.

RETURN VALUE        top

       Theinitgroups() function returns 0 on success.  On error, -1 is       returned, anderrno is set to indicate the error.

ERRORS        top

ENOMEMInsufficient memory to allocate group information              structure.EPERMThe calling process has insufficient privilege.  See the              underlying system callsetgroups(2).

FILES        top

/etc/group              group database file

ATTRIBUTES        top

       For an explanation of the terms used in this section, seeattributes(7).       ┌───────────────────────────────┬───────────────┬────────────────┐       │Interface│Attribute│Value│       ├───────────────────────────────┼───────────────┼────────────────┤       │initgroups()                  │ Thread safety │ MT-Safe locale │       └───────────────────────────────┴───────────────┴────────────────┘

STANDARDS        top

       None.

HISTORY        top

       SVr4, 4.3BSD.

SEE ALSO        top

getgroups(2),setgroups(2),credentials(7)

COLOPHON        top

       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            2025-05-17initgroups(3)

Pages that refer to this page:groups(1@@shadow-utils), getgroups(2), group(5), nss(5), credentials(7)

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