getgrgid(3)
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(), Thread safety MT-Safe locale getgrgid_r()
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 4.09 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/.
2016-03-15 GETGRNAM(3)
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