getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry
Standard C library (libc, -lc)
#include <sys/types.h>
#include <grp.h>
struct group *getgrnam(const char *name);
struct group *getgrgid(gid_t gid);
int getgrnam_r(const char *restrict name, struct group *restrict grp,
char buf[restrict .buflen], size_t buflen,
struct group **restrict result);
int getgrgid_r(gid_t gid, struct group *restrict grp,
char buf[restrict .buflen], size_t buflen,
struct group **restrict result);Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
getgrnam_r(), getgrgid_r():
_POSIX_C_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCEThe 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 to indicate the error. 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.
The given name or gid was not found.
A signal was caught; see signal(7).
I/O error.
The per-process limit on the number of open file descriptors has been reached.
The system-wide limit on the total number of open files has been reached.
Insufficient memory to allocate group structure.
Insufficient buffer space supplied.
/etc/grouplocal 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 |
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.
POSIX.1-2008.
POSIX.1-2001, SVr4, 4.3BSD.