getgrent(3) - Linux manual page (original) (raw)
getgrent(3) Library Functions Manual getgrent(3)
NAME top
getgrent, setgrent, endgrent - get group file entryLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#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_SOURCEDESCRIPTION top
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)](../man5/group.5.html).RETURN VALUE top
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](../man3/errno.3.html)_ may be set. If one wants to check _[errno](../man3/errno.3.html)_ 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)](../man3/getgrgid.3.html), or
[getgrnam(3)](../man3/getgrnam.3.html). (Do not pass the returned pointer to [free(3)](../man3/free.3.html).)ERRORS top
**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)](../man7/signal.7.html).
**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 top
_/etc/group_
local group database fileATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌─────────────┬───────────────┬──────────────────────────────────┐
│ **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 top
POSIX.1-2008.HISTORY top
POSIX.1-2001, SVr4, 4.3BSD.SEE ALSO top
[fgetgrent(3)](../man3/fgetgrent.3.html), [getgrent_r(3)](../man3/getgrent%5Fr.3.html), [getgrgid(3)](../man3/getgrgid.3.html), [getgrnam(3)](../man3/getgrnam.3.html),
[getgrouplist(3)](../man3/getgrouplist.3.html), [putgrent(3)](../man3/putgrent.3.html), [group(5)](../man5/group.5.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 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)