GETGRNAM(3) Linux Programmer's Manual GETGRNAM(3)
NAME
getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry
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 *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
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
members of the group structure are stored in the buffer buf of size bu-
flen. 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 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 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 at-
tributes(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() | | |
+--------------+---------------+-----------------------------+
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
NOTES
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 sit-
uation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably oth-
ers.
SEE ALSO
endgrent(3), fgetgrent(3), getgrent(3), getpwnam(3), setgrent(3),
group(5)
COLOPHON
This page is part of release 5.07 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 GETGRNAM(3)