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.\" $OpenBSD: getgrent.3,v 1.16 2008/07/28 20:19:32 jmc 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. 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.
.\"
.Dd $Mdocdate: July 28 2008 $
.Dt GETGRENT 3
.Os
.Sh NAME
.Nm getgrent ,
.Nm getgrnam ,
.Nm getgrnam_r ,
.Nm getgrgid ,
.Nm getgrgid_r ,
.Nm setgroupent ,
.\" .Nm setgrfile ,
.Nm setgrent ,
.Nm endgrent
.Nd group database operations
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <grp.h>
.Ft struct group *
.Fn getgrent void
.Ft struct group *
.Fn getgrnam "const char *name"
.Ft int
.Fn getgrnam_r "const char *name" "struct group *grp" "char *buffer" "size_t bufsize" "struct group **result"
.Ft struct group *
.Fn getgrgid "gid_t gid"
.Ft int
.Fn getgrgid_r "gid_t gid" "struct group *grp" "char *buffer" "size_t bufsize" "struct group **result"
.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
.Pa /etc/group
which is described
in
.Xr group 5 .
Each line of the database is defined by the structure
.Li struct 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
.Fa name
or the group ID pointed to by
.Fa gid ,
respectively, returning the first one encountered.
Identical group names or group GIDs may result in undefined behavior.
.Pp
.Fn getgrent
sequentially reads the group database and is intended for programs
that wish to step through the complete list of groups.
.Pp
All three routines will open the group file for reading, if necessary.
.Pp
.Fn setgroupent
opens the file, or rewinds it if it is already open.
If
.Fa stayopen
is non-zero, file descriptors are left open, significantly speeding
subsequent function 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
.Fn setgrent
is equivalent to
.Fn setgroupent
with an argument of zero.
.Pp
The
.Fn endgrent
function closes any open files.
.Pp
The
.Fn getgrgid_r
and
.Fn getgrnam_r
functions both update the group structure pointed to by
.Fa grp
and store a pointer to that structure at the location pointed to by
.Fa result .
The structure is filled with an entry from the group database with a
matching
.Fa gid
or
.Fa name .
Storage referenced by the group structure will be allocated from the memory
provided with the
.Fa buffer
parameter, which is
.Fa bufsiz
characters in size.
.\" The maximum size needed for this buffer can be determined with the
.\" .Dv _SC_GETGR_R_SIZE_MAX
.\" .Xr sysconf 2
.\" parameter.
.Sh YP SUPPORT
If YP is active, the functions
.Fn getgrent
and
.Fn getgrnam
also use the
.Pa group.byname
YP map and the function
.Fn getgrgid
also uses the
.Pa group.bygid
YP map in addition to the group file,
respecting the order of normal and YP entries in the group file.
.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 0.
The
.Fn endgrent
and
.Fn setgrent
functions have no return value.
The functions
.Fn getgrgid_r
and
.Fn getgrnam_r
store a null pointer at the location pointed to by
.Fa result
and return the error number
if an error occurs, or the requested entry is not found.
.Sh FILES
.Bl -tag -width /etc/group -compact
.It Pa /etc/group
group database file
.El
.Sh SEE ALSO
.Xr getpwent 3 ,
.Xr ypclnt 3 ,
.Xr group 5 ,
.Xr yp 8
.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 .
.Pp
The historic function
.Xr setgrfile 3 ,
which allowed the specification of alternate group 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.
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