initgroups man page

initgroups — initialize the supplementary group access list


#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)):

   Since glibc 2.19:
   Glibc 2.19 and earlier:


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.



Insufficient memory to allocate group information structure.


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


/etc/group		group database file


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)


This page is part of release 4.13 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

Referenced By

credentials(7), getgroups(2), group(5), nss(5), setpriv(1), slapd(8).

2017-09-15 GNU Linux Programmer's Manual