initgroups(3) — Linux manual page

initgroups(3)            Library Functions Manual           initgroups(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_t group);

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       initgroups():
           Since glibc 2.19:
               _DEFAULT_SOURCE
           glibc 2.19 and earlier:
               _BSD_SOURCE

DESCRIPTION         top

       The initgroups() function initializes the group access list by
       reading the group database /etc/group and using all groups of
       which user is a member.  The additional group group is also added
       to the list.

       The user argument must be non-NULL.

RETURN VALUE         top

       The initgroups() function returns 0 on success.  On error, -1 is
       returned, and errno is set to indicate the error.

ERRORS         top

       ENOMEM Insufficient memory to allocate group information
              structure.

       EPERM  The calling process has insufficient privilege.  See the
              underlying system call setgroups(2).

FILES         top

       /etc/group
              group database file

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(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

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Linux man-pages 6.15            2025-05-17                  initgroups(3)

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

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