.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)

.\"

.\" %%%LICENSE_START(VERBATIM)

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.\" manual provided the copyright notice and this permission notice are

.\" preserved on all copies.

.\"

.\" Permission is granted to copy and distribute modified versions of this

.\" manual under the conditions for verbatim copying, provided that the

.\" entire resulting derived work is distributed under the terms of a

.\" permission notice identical to this one.

.\"

.\" Since the Linux kernel and libraries are constantly changing, this

.\" manual page may be incorrect or out-of-date.  The author(s) assume no

.\" responsibility for errors or omissions, or for damages resulting from

.\" the use of the information contained herein.  The author(s) may not

.\" have taken the same level of care in the production of this manual,

.\" which is licensed free of charge, as they might when working

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.\" Formatted or processed versions of this manual, if unaccompanied by

.\" the source, must acknowledge the copyright and authors of this work.

.\" %%%LICENSE_END

.\"

.\" References consulted:

.\"     Linux libc source code

.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)

.\"     386BSD man pages

.\" Modified Sat Jul 24 19:29:54 1993 by Rik Faith (faith@cs.unc.edu)

.TH GETGRENT 3  2017-09-15 "" "Linux Programmer's Manual"

.SH NAME

getgrent, setgrent, endgrent \- get group file entry

.SH SYNOPSIS

.nf

.B #include <sys/types.h>

.B #include <grp.h>

.PP

.B struct group *getgrent(void);

.PP

.B void setgrent(void);

.PP

.B void endgrent(void);

.fi

.PP

.in -4n

Feature Test Macro Requirements for glibc (see

.BR feature_test_macros (7)):

.in

.PP

.PD 0

.ad l

.BR setgrent ():

.RS 4

_XOPEN_SOURCE\ >=\ 500

.\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED

    || /* Glibc since 2.19: */ _DEFAULT_SOURCE

    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

.RE

.PP

.BR getgrent (),

.BR endgrent ():

.RS 4

Since glibc 2.22:

    _XOPEN_SOURCE\ >=\ 500 ||

.\"        || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED

        _DEFAULT_SOURCE

.br

Glibc 2.21 and earlier

    _XOPEN_SOURCE\ >=\ 500

.\"        || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED

        || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L

        || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

.RE

.PD

.ad b

.SH DESCRIPTION

The

.BR getgrent ()

function returns a pointer to a structure containing

the broken-out fields of a record in the group database

(e.g., the local group file

.IR /etc/group ,

NIS, and LDAP).

The first time

.BR getgrent ()

is called,

it returns the first entry; thereafter, it returns successive entries.

.PP

The

.BR setgrent ()

function rewinds to the beginning

of the group database, to allow repeated scans.

.PP

The

.BR endgrent ()

function is used to close the group database

after all processing has been performed.

.PP

The \fIgroup\fP structure is defined in \fI<grp.h>\fP as follows:

.PP

.in +4n

.EX

struct group {

    char   *gr_name;        /* group name */

    char   *gr_passwd;      /* group password */

    gid_t   gr_gid;         /* group ID */

    char  **gr_mem;         /* NULL-terminated array of pointers

                               to names of group members */

};

.EE

.in

.PP

For more information about the fields of this structure, see

.BR group (5).

.SH RETURN VALUE

The

.BR getgrent ()

function returns a pointer to a

.I group

structure,

or NULL if there are no more entries or an error occurs.

.PP

Upon error,

.I errno

may be set.

If one wants to check

.I errno

after the call, it should be set to zero before the call.

.PP

The return value may point to a static area, and may be overwritten

by subsequent calls to

.BR getgrent (),

.BR getgrgid (3),

or

.BR getgrnam (3).

(Do not pass the returned pointer to

.BR free (3).)

.SH ERRORS

.TP

.B EAGAIN

The service was temporarily unavailable; try again later.

For NSS backends in glibc this indicates a temporary error talking to the backend.

The error may correct itself, retrying later is suggested.

.TP

.B EINTR

A signal was caught; see

.BR signal (7).

.TP

.B EIO

I/O error.

.TP

.B EMFILE

The per-process limit on the number of open file descriptors has been reached.

.TP

.B ENFILE

The system-wide limit on the total number of open files has been reached.

.TP

.\" not in POSIX

.B ENOENT

A necessary input file cannot be found.

For NSS backends in glibc this indicates the backend is not correctly configured.

.TP

.B ENOMEM

.\" not in POSIX

Insufficient memory to allocate

.I group

structure.

.TP

.B ERANGE

Insufficient buffer space supplied.

.SH FILES

.TP

.I /etc/group

local group database file

.SH ATTRIBUTES

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

.BR attributes (7).

.TS

allbox;

lbw11 lb lb

l l l.

Interface	Attribute	Value

T{

.BR getgrent ()

T}	Thread safety	T{

MT-Unsafe race:grent

.br

race:grentbuf locale

T}

T{

.BR setgrent (),

.BR endgrent ()

T}	Thread safety	MT-Unsafe race:grent locale

.TE

.PP

In the above table,

.I grent

in

.I race:grent

signifies that if any of the functions

.BR setgrent (),

.BR getgrent (),

or

.BR endgrent ()

are used in parallel in different threads of a program,

then data races could occur.

.SH CONFORMING TO

POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

.SH SEE ALSO

.BR fgetgrent (3),

.BR getgrent_r (3),

.BR getgrgid (3),

.BR getgrnam (3),

.BR getgrouplist (3),

.BR putgrent (3),

.BR group (5)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I 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/.