getgrent
Section: C Library Functions (3)
Updated: 202-0-08
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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 broke-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 pe-process limit on the number of open file descriptors has been reached.
- ENFILE
-
The syste-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 |
M-Unsafe race:grent
race:grentbuf locale
|
|
setgrent(),
endgrent()
| Thread safety |
M-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.
STANDARDS
POSIX.-2008.
HISTORY
POSIX.-2001, SVr4, 4.3BSD.
SEE ALSO
fgetgrent(3),
getgrent_r(3),
getgrgid(3),
getgrnam(3),
getgrouplist(3),
putgrent(3),
group(5)
Index
- NAME
-
- LIBRARY
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- FILES
-
- ATTRIBUTES
-
- STANDARDS
-
- HISTORY
-
- SEE ALSO
-
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