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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | FILES | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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getgrent(3) Library Functions Manual getgrent(3)
getgrent, setgrent, endgrent - get group file entry
Standard C library (libc, -lc)
#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
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).
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).)
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.
/etc/group
local group database file
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.
POSIX.1-2008.
POSIX.1-2001, SVr4, 4.3BSD.
fgetgrent(3), getgrent_r(3), getgrgid(3), getgrnam(3),
getgrouplist(3), putgrent(3), group(5)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 getgrent(3)
Pages that refer to this page: getent(1), pmcd(1), pmdapipe(1), fgetgrent(3), getgrent_r(3), getgrnam(3), getgrouplist(3), putgrent(3), setaliasent(3), group(5), nss(5), nsswitch.conf(5)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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