getgrent man page

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);

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).

InterfaceAttributeValue
getgrent()Thread safetyMT-Unsafe race:grent
race:grentbuf locale
setgrent(), endgrent()Thread safetyMT-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.

See Also

fgetgrent(3), getgrent_r(3), getgrgid(3), getgrnam(3), getgrouplist(3), putgrent(3), group(5)

Colophon

This page is part of release 4.08 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/.

Referenced By

explain(1), explain(3), explain_endgrent(3), explain_endgrent_or_die(3), explain_getgrent(3), explain_getgrent_or_die(3), explain_setgrent(3), explain_setgrent_or_die(3), fgetgrent(3), gentoo(1), getent(1), getgrent_r(3), getgrnam(3), getgrouplist(3), group(5), hlfsd(8), mh-alias(5), nss(5), nsswitch.conf(5), pmcd(1), pmdapipe(1), putgrent(3), setaliasent(3), winbindd(8).

endgrent(3) and setgrent(3) are aliases of getgrent(3).

2016-03-15 Linux Programmer's Manual