| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | FILES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON | The Linux Programming Interface |
GETGRNAM(3) Linux Programmer's Manual GETGRNAM(3)
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 *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 >= 1 || _XOPEN_SOURCE || _BSD_SOURCE ||
_SVID_SOURCE || _POSIX_SOURCE
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; /* 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.)
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.
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.
/etc/group
local group database file
SVr4, 4.3BSD, POSIX.1-2001.
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)
This page is part of release 3.51 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/.
2012-04-23 GETGRNAM(3)
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