Provided by: manpages-dev_5.05-1_all 
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);
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():
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 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(), │ 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.
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 5.05 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/.
2017-09-15 GETGRENT(3)