posix man page for initgroups

INITGROUPS(3)						     Linux Programmer's Manual						     INITGROUPS(3)

NAME
       initgroups - initialize the supplementary group access list

SYNOPSIS
       #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
       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
       The initgroups() function returns 0 on success.	On error, -1 is returned, and errno is set appropriately.

ERRORS
       ENOMEM Insufficient memory to allocate group information structure.

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

FILES
       /etc/group
	      group database file

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       +-------------+---------------+----------------+
       |Interface    | Attribute     | Value	      |
       +-------------+---------------+----------------+
       |initgroups() | Thread safety | MT-Safe locale |
       +-------------+---------------+----------------+

CONFORMING TO
       SVr4, 4.3BSD.

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

COLOPHON
       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

GNU
								    2017-09-15							     INITGROUPS(3)