man3/initgroups.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
.\" Modified 2004-10-10 by aeb
.\"
.TH INITGROUPS 3  2017-09-15 "GNU" "Linux Programmer's Manual"
.SH NAME
initgroups \- initialize the supplementary group access list
.SH SYNOPSIS
.nf
.B #include <sys/types.h>
.B #include <grp.h>
.PP
.BI "int initgroups(const char *" user ", gid_t " group );
.fi
.PP
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.PP
.BR initgroups ():
    Since glibc 2.19:
        _DEFAULT_SOURCE
    Glibc 2.19 and earlier:
        _BSD_SOURCE
.SH DESCRIPTION
The
.BR initgroups ()
function initializes the group access list by
reading the group database
.I /etc/group
and using all groups of
which
.I user
is a member.
The additional group
.I group
is
also added to the list.
.PP
The
.I user
argument must be non-NULL.
.SH RETURN VALUE
The
.BR initgroups ()
function returns 0 on success.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B ENOMEM
Insufficient memory to allocate group information structure.
.TP
.B EPERM
The calling process has insufficient privilege.
See the underlying system call
.BR setgroups (2).
.SH FILES
.TP
.I /etc/group
group database file
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lb lb lb
l l l.
Interface	Attribute	Value
T{
.BR initgroups ()
T}	Thread safety	MT-Safe locale
.TE
.sp 1
.SH CONFORMING TO
SVr4, 4.3BSD.
.SH SEE ALSO
.BR getgroups (2),
.BR setgroups (2),
.BR credentials (7)