getgrent(3) — Linux manual pages

Linux manual pages	Section 3

Name

getgrent, setgrent, endgrent — get group file entry

Synopsis

#include <sys/types.h>
#include <grp.h>

struct group *getgrent( void);

void setgrent( void);

void endgrent( void);

Note

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
`setgrent`():
`_SVID_SOURCE` \|\| `_BSD_SOURCE` \|\| `_XOPEN_SOURCE` >= 500 \|\| `_XOPEN_SOURCE` && `_XOPEN_SOURCE_EXTENDED` \|\|
/* Since glibc 2.12:
*/ `_POSIX_C_SOURCE` >= 200809L
`getgrent`(), `endgrent`():
`_SVID_SOURCE` \|\| `_BSD_SOURCE` \|\| `_XOPEN_SOURCE` >= 500 \|\| `_XOPEN_SOURCE` && `_XOPEN_SOURCE_EXTENDED`

DESCRIPTION

The 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 /etc/group, NIS, and LDAP). The first time getgrent() is called, it returns the first entry; thereafter, it returns successive entries.

The setgrent() function rewinds to the beginning of the group database, to allow repeated scans.

The endgrent() function is used to close the group database after all processing has been performed.

The group structure is defined in <grp.h> as follows:

struct group {

char * gr_name;
/* group name */

char * gr_passwd;
/* group password */

gid_t gr_gid;
/* group ID */

char ** gr_mem;
/* group members */

};

For more information about the fields of this structure, see group(5).

RETURN VALUE

The getgrent() function returns a pointer to a group structure, or NULL if there are no more entries or an error occurs.

Upon error, errno may be set. If one wants to check errno after the call, it should be set to zero before the call.

The return value may point to a static area, and may be overwritten by subsequent calls to getgrent(), getgrgid(3), or getgrnam(3). (Do not pass the returned pointer to free(3).)

ERRORS

EINTR: A signal was caught.
EIO: I/O error.
EMFILE: The calling process already has too many open files.
ENFILE: Too many open files in the system.
ENOMEM: Insufficient memory to allocate group structure.
ERANGE: Insufficient buffer space supplied.

FILES

/etc/group: local group database file

CONFORMING TO

SVr4, 4.3BSD, POSIX.1-2001.

COLOPHON

This page is part of release 3.33 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://man7.org/linux/man-pages/.

  Copyright 1993 David Metcalfe (davidprism.demon.co.uk)

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

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manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
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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
professionally.

Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.

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 (faithcs.unc.edu)

struct	group {
	char	*	`gr_name`;	/* group name */
	char	*	`gr_passwd`;	/* group password */
	gid_t		`gr_gid`;	/* group ID */
	char	**	`gr_mem`;	/* group members */
};