GETGRNAM
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
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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
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 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 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.
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(),
getgrgid_r()
| Thread safety | MT-Safe locale
|
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
situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably others.
SEE ALSO
endgrent(3),
fgetgrent(3),
getgrent(3),
getpwnam(3),
setgrent(3),
group(5)
COLOPHON
This page is part of release 4.13 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/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- FILES
-
- ATTRIBUTES
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
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- Running on 
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