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
getgrnam_r()
and
getgrgid_r()
functions obtain the same information, but store the retrieved
group
structure
in the space pointed to by
grp.
This
group
structure contains pointers to strings, and these strings
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 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; /* group members */
};
The maximum needed size for
buf
can be found using
sysconf(3)
with the argument
_SC_GETGR_R_SIZE_MAX.
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 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 static area, and may be overwritten
by subsequent calls to
getgrent(3),
getgrgid(),
or
getgrnam().
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.
ERRORS
0 or ENOENT or ESRCH or EBADF or EPERM or ...
The given
name
or
gid
was not found.
EINTR
A signal was caught.
EIO
I/O error.
EMFILE
The maximum number
(OPEN_MAX)
of files was open already in the calling process.
ENFILE
The maximum number of files was open already in the system.
ENOMEM
Insufficient memory to allocate
group
structure.
ERANGE
Insufficient buffer space supplied.
FILES
/etc/group
local group database file
CONFORMING TO
SVr4, 4.3BSD, POSIX.1-2001.
NOTES
The formulation given above under "RETURN VALUE" is from POSIX.1-2001.
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 shows that lots of different values occur in this
situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and probably others.
This page is part of release 3.14 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
