getgrent(3) Library Functions Manual getgrent(3)
NAME
getgrent, setgrent, endgrent - get group file entry
LIBRARY
Standard C library (libc, -lc)
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 >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
getgrent(), endgrent():
Since glibc 2.22:
_XOPEN_SOURCE >= 500 || _DEFAULT_SOURCE
glibc 2.21 and earlier
_XOPEN_SOURCE >= 500
|| /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
|| /* glibc <= 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(), │ Thread safety │ MT-Unsafe race:grent locale │
│ endgrent() │ │ │
└─────────────┴───────────────┴────────────────────────────────────────┘
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.
STANDARDS
POSIX.1-2008.
HISTORY
POSIX.1-2001, SVr4, 4.3BSD.
SEE ALSO
fgetgrent(3), getgrent_r(3), getgrgid(3), getgrnam(3), getgrouplist(3),
putgrent(3), group(5)
Linux man-pages 6.9.1 2024-05-02 getgrent(3)
Generated by dwww version 1.16 on Tue Dec 16 04:35:08 CET 2025.