getgrnam(3) Library Functions Manual getgrnam(3)
NAME
getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#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_SOURCE
DESCRIPTION
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 mem-
bers 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.)
RETURN VALUE
The getgrnam() and getgrgid() functions return a pointer to a group
structure, or NULL if the matching entry is not found or an error oc-
curs. 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 re-
turned, and NULL is stored in *result.
ERRORS
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.
FILES
/etc/group
local group database file
ATTRIBUTES
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(), │ Thread safety │ MT-Safe locale │
│ getgrgid_r() │ │ │
└───────────────┴───────────────┴──────────────────────────────────────┘
VERSIONS
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 situ-
ation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably others.
STANDARDS
POSIX.1-2008.
HISTORY
POSIX.1-2001, SVr4, 4.3BSD.
SEE ALSO
endgrent(3), fgetgrent(3), getgrent(3), getpwnam(3), setgrent(3),
group(5)
Linux man-pages 6.9.1 2024-05-02 getgrnam(3)
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