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 * | gbuf, | |
char * | buf, | |
size_t | buflen, | |
struct group ** | gbufp) ; |
int
getgrgid_r( |
gid_t | gid, |
struct group * | gbuf, | |
char * | buf, | |
size_t | buflen, | |
struct group ** | gbufp) ; |
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 gbuf
.
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 *gbufp
.
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
_SC_GETGR_R_SIZE_MAX parameter.
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
().
The getgrnam_r
() and
getgrgid_r
() functions return
zero on success. In case of error, an error number is
returned.
0
or
ENOENT or ESRCH or EBADF or EPERM or ...The given name
or gid
was not found.
A signal was caught.
I/O error.
The maximum number (OPEN_MAX) of files was open already in the calling process.
The maximum number of files was open already in the system.
Insufficient memory to allocate group structure.
Insufficient buffer space supplied.
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.
endgrent(3), fgetgrent(3), getgrent(3), getpwnam(3), setgrent(3), group(5)
|