libc/gen/getgrent.3

.\"	$NetBSD: getgrent.3,v 1.17 2002/10/01 16:48:34 wiz Exp $
.\"
.\" Copyright (c) 1989, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)getgrent.3	8.2 (Berkeley) 4/19/94
.\"
.Dd April 25, 1999
.Dt GETGRENT 3
.Os
.Sh NAME
.Nm getgrent ,
.Nm getgrnam ,
.Nm getgrgid ,
.Nm setgroupent ,
.\" .Nm setgrfile ,
.Nm setgrent ,
.Nm endgrent
.Nd group database operations
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd #include \*[Lt]grp.h\*[Gt]
.Ft struct group *
.Fn getgrent void
.Ft struct group *
.Fn getgrnam "const char *name"
.Ft struct group *
.Fn getgrgid "gid_t gid"
.Ft int
.Fn setgroupent "int stayopen"
.\" .Ft void
.\" .Fn setgrfile "const char *name"
.Ft void
.Fn setgrent void
.Ft void
.Fn endgrent void
.Sh DESCRIPTION
These functions operate on the group database file which is described in
.Xr group 5 .
Each line of the database is defined by the structure
.Ar group
found in the include
file
.Aq Pa grp.h :
.Bd -literal -offset indent
struct group {
	char	*gr_name;	/* group name */
	char	*gr_passwd;	/* group password */
	gid_t	gr_gid;		/* group id */
	char	**gr_mem;	/* group members */
};
.Ed
.Pp
The functions
.Fn getgrnam
and
.Fn getgrgid
search the group database for the given group name pointed to by
.Ar name
or the group id pointed to by
.Ar gid ,
respectively, returning the first one encountered.
Identical group names or group gids may result in undefined behavior.
.Pp
The
.Fn getgrent
function sequentially reads the group database and is intended for programs
that wish to step through the complete list of groups.
.Pp
All three functions will open the group file for reading, if necessary.
.Pp
The
.Fn setgroupent
function opens the file, or rewinds it if it is already open.
If
.Fa stayopen
is non-zero, file descriptors are left open, significantly speeding
functions subsequent calls.
This functionality is unnecessary for
.Fn getgrent
as it doesn't 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.
.Pp
The
.Fn setgrent
function is equivalent to
.Fn setgroupent
with an argument of zero.
.Pp
The
.Fn endgrent
function closes any open files.
.Sh RETURN VALUES
The functions
.Fn getgrent ,
.Fn getgrnam ,
and
.Fn getgrgid ,
return a pointer to the group entry if successful; if end-of-file
is reached or an error occurs a null pointer is returned.
The
.Fn setgroupent
function returns the value 1 if successful, otherwise the value
0 is returned.
The
.Fn endgrent
and
.Fn setgrent
functions have no return value.
.Sh FILES
.Bl -tag -width /etc/group -compact
.It Pa /etc/group
group database file
.El
.Sh SEE ALSO
.Xr getpwent 3 ,
.Xr group 5 ,
.Xr nsswitch.conf 5
.Sh STANDARDS
The
.Fn getgrnam
and
.Fn getgrgid
functions conform to
.St -p1003.1-90 .
.Sh HISTORY
The functions
.Fn endgrent ,
.Fn getgrent ,
.Fn getgrnam ,
.Fn getgrgid ,
and
.Fn setgrent
appeared in
.At v7 .
The functions
.Fn setgrfile
and
.Fn setgroupent
appeared in
.Bx 4.3 Reno .
.Sh COMPATIBILITY
The historic function
.Fn setgrfile ,
which allowed the specification of alternative password databases, has
been deprecated and is no longer available.
.Sh BUGS
The functions
.Fn getgrent ,
.Fn getgrnam ,
.Fn getgrgid ,
.Fn setgroupent
and
.Fn setgrent
leave their results in an internal static object and return
a pointer to that object.
Subsequent calls to the same function will modify the same object.
.Pp
The functions
.Fn getgrent ,
.Fn endgrent ,
.Fn setgroupent ,
and
.Fn setgrent
are fairly useless in a networked environment and should be
avoided, if possible.
.Fn getgrent
makes no attempt to suppress duplicate information if multiple
sources are specified in
.Xr nsswitch.conf 5