getgrent(3) BSD Library Functions Manual getgrent(3)
NAME
getgrent, getgrnam, getgrnam_r, getgrgid, getgrgid_r, getgruuid,
getgruuid_r, setgroupent, setgrent, endgrent -- group database operations
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <grp.h>
#include <uuid/uuid.h>
struct group *
getgrent(void);
struct group *
getgrnam(const char *name);
int
getgrnam_r(const char *name, struct group *grp, char *buffer,
size_t bufsize, struct group **result);
struct group *
getgrgid(gid_t gid);
int
getgrgid_r(gid_t gid, struct group *grp, char *buffer, size_t bufsize,
struct group **result);
int
getgruuid(uuid_t uuid);
int
getgruuid_r(uuid_t uuid, struct group *grp, char *buffer, size_t bufsize,
struct group **result);
int
setgroupent(int stayopen);
void
setgrent(void);
void
endgrent(void);
DESCRIPTION
These functions obtain information from opendirectoryd(8), including
records in /etc/group which is described in group(5). Each line of the
database is defined by the structure group found in the include file
<grp.h>:
struct group {
char *gr_name; /* group name */
char *gr_passwd; /* group password */
gid_t gr_gid; /* group id */
char **gr_mem; /* group members */
};
The functions getgrnam(), getgrgid(), and getgruuid() search the group
database for the given group name pointed to by name, the group id given
by gid, or the UUID given by uuid respectively, returning the first one
encountered. Identical group names, group gids, or uuids may result in
undefined behavior.
Note that the groups file /etc/group does not contain group UUIDs. The
UUID for a group may be found using mbr_gid_to_uuid().
On Mac OS X, these routines are thread-safe and return a pointer to a
thread-specific data structure. The contents of this data structure are
automatically released by subsequent calls to any of these routines on
the same thread, or when the thread exits. These routines are therefore
unsuitable for use in libraries or frameworks, from where they may over-
write the per-thread data that the calling application expects to find as
a result of its own calls to these routines. Library and framework code
should use the alternative reentrant variants detailed below.
The getgrent() function sequentially reads the group database and is
intended for programs that wish to step through the complete list of
groups.
The functions getgrnam_r(), getgrgid_r(), and getgruuid_r() are alterna-
tive versions of getgrnam(), getgrgid(), and getgruuid() respectively.
The caller must provide storage for the results of the search in the grp,
buffer, bufsize, and result arguments. When these functions are success-
ful, the grp argument will be filled-in, and a pointer to that argument
will be stored in result. If an entry is not found or an error occurs,
result will be set to NULL.
These functions will open the group file for reading, if necessary.
The setgroupent() function opens the file, or rewinds it if it is already
open. If stayopen is non-zero, file descriptors are left open, signifi-
cantly speeding functions subsequent calls. This functionality is unnec-
essary for getgrent() as it does not close its file descriptors by
default. It should also be noted that it is dangerous for long-running
programs to use this functionality as the group file may be updated.
The setgrent() function is identical to setgroupent() with an argument of
zero.
The endgrent() function closes any open files.
RETURN VALUES
The functions getgrent(), getgrnam(), and getgrgid(), return a pointer to
a group structure on success or NULL if the entry is not found or if an
error occurs. If an error does occur, errno will be set. Note that pro-
grams must explicitly set errno to zero before calling any of these func-
tions if they need to distinguish between a non-existent entry and an
error. The functions getgrnam_r(), getgrgid_r(), and getgruuid_r()
return 0 if no error occurred, or an error number to indicate failure.
It is not an error if a matching entry is not found. (Thus, if result is
set to NULL and the return value is 0, no matching entry exists.)
setgroupent() returns the value 1 if successful, otherwise the value 0 is
returned. The functions setgrent(), endgrent(), and setgrfile() have no
return value.
FILES
/etc/group group database file
COMPATIBILITY
The historic function setgrfile(), which allowed the specification of
alternate group databases, has been deprecated and is no longer avail-
able.
SEE ALSO
getpwent(3), group(5), mbr_gid_to_uuid(3,) opendirectory(8), yp(8)
STANDARDS
The getgrent(), getgrnam(), getgrnam_r(), getgrgid(), getgrgid_r() and
endgrent() functions conform to ISO/IEC 9945-1:1996 (``POSIX.1''). The
setgrent() function differs from that standard in that its return type is
int rather than void.
HISTORY
The functions endgrent(), getgrent(), getgrnam(), getgrgid(), and
setgrent() appeared in Version 7 AT&T UNIX. The functions setgrfile()
and setgroupent() appeared in 4.3BSD-Reno. The functions getgrnam_r()
and getgrgid_r() appeared in FreeBSD 5.1. The functions getgruuid() and
getgruuid_r() appeared in Mac OS X 10.8.
BUGS
The functions getgrent(), getgrnam(), getgrgid(), getgruuid(),
setgroupent() and setgrent() leave their results in an internal thread-
specific memory and return a pointer to that object. Subsequent calls to
the same function will modify the same object.
BSD October 26, 2011 BSD
Mac OS X 10.8 - Generated Sat Aug 25 18:17:06 CDT 2012