getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry
#include <sys/types.h>
#include <grp.h>
struct group *getgrnam(const char *name);
struct group *getgrgid(gid_t gid);
int getgrnam_r(const char *name, struct group *grp,
char *buf, size_t buflen, struct group **result);
int getgrgid_r(gid_t gid, struct group *grp,
char *buf, size_t buflen, struct group **result);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
getgrnam_r(),
getgrgid_r():
_POSIX_C_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
The
getgrnam() function returns a pointer to a structure containing the
broken-out fields of the record in the group database (e.g., the local group
file
/etc/group, NIS, and LDAP) that matches the group name
name.
The
getgrgid() function returns a pointer to a structure containing the
broken-out fields of the record in the group database that matches the group
ID
gid.
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
getgrnam_r() and
getgrgid_r() functions obtain the same
information as
getgrnam() and
getgrgid(), but store the
retrieved
group structure in the space pointed to by
grp. The
string fields pointed to by the members of the
group structure are
stored in the buffer
buf of size
buflen. A pointer to the result
(in case of success) or NULL (in case no entry was found or an error occurred)
is stored in
*result.
The call
sysconf(_SC_GETGR_R_SIZE_MAX)
returns either -1, without changing
errno, or an initial suggested size
for
buf. (If this size is too small, the call fails with
ERANGE,
in which case the caller can retry with a larger buffer.)
The
getgrnam() and
getgrgid() functions return a pointer to a
group structure, or NULL if the matching entry is not found or an error
occurs. If an error occurs,
errno is set appropriately. 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(3),
getgrgid(), or
getgrnam(). (Do not pass the returned pointer to
free(3).)
On success,
getgrnam_r() and
getgrgid_r() return zero, and set
*result to
grp. If no matching group record was found, these
functions return 0 and store NULL in
*result. In case of error, an
error number is returned, and NULL is stored in
*result.
- 0 or ENOENT or ESRCH or EBADF or EPERM
or ...
- The given name or gid was not found.
- 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.
- 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 |
getgrnam () |
Thread safety |
MT-Unsafe race:grnam locale |
getgrgid () |
Thread safety |
MT-Unsafe race:grgid locale |
getgrnam_r (), getgrgid_r () |
Thread safety |
MT-Safe locale |
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
The formulation given above under "RETURN VALUE" is from POSIX.1. It
does not call "not found" an error, hence does not specify what
value
errno might have in this situation. But that makes it impossible
to recognize errors. One might argue that according to POSIX
errno
should be left unchanged if an entry is not found. Experiments on various
UNIX-like systems show that lots of different values occur in this situation:
0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably others.
endgrent(3),
fgetgrent(3),
getgrent(3),
getpwnam(3),
setgrent(3),
group(5)