| 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 maximum needed size for buf can be found using sysconf(3) with the
argument _SC_GETGR_R_SIZE_MAX.
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 3.32 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/.
2010-10-21 GETGRNAM(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface