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`():
`_XOPEN_SOURCE` >= 500 \|\| /* Glibc since 2.19:
/ `_DEFAULT_SOURCE` \|\| / Glibc versions <= 2.19:
*/ `_BSD_SOURCE` \|\| `_SVID_SOURCE`
`getgrent`(), `endgrent`():
`_XOPEN_SOURCE` >= 500 \|\| /* Since glibc 2.12:
/ `_POSIX_C_SOURCE` >= 200809L \|\| / Glibc versions <= 2.19:
*/ `_BSD_SOURCE` \|\| `_SVID_SOURCE`

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;
/* NULL-terminated array of pointers
to names of 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

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.
EINTR: A signal was caught; see signal(7).
EIO: I/O error.
EMFILE: The per-process limit on the number of open file descriptors has been reached.
ENFILE: The system-wide limit on the total number of open files has been reached.
ENOENT: A necessary input file cannot be found. For NSS backends in glibc this indicates the backend is not correctly configured.
ENOMEM: Insufficient memory to allocate group structure.
ERANGE: Insufficient buffer space supplied.

FILES

/etc/group: local group database file

ATTRIBUTES

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

Interface Attribute Value

getgrent()

Thread safety

MT-Unsafe race:grent

race:grentbuf locale

setgrent(), endgrent() Thread safety MT-Unsafe race:grent locale

In the above table, grent in race:grent signifies that if any of the functions setgrent(), getgrent(), or endgrent() are used in parallel in different threads of a program, then data races could occur.

CONFORMING TO

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

COLOPHON

This page is part of release 4.07 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/.

  Copyright 1993 David Metcalfe (davidprism.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 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`;	/* NULL-terminated array of pointers to names of group members */
};