gno/usr.man/man3/getgrent.3

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.\"     From: @(#)getgrent.3	8.2 (Berkeley) 4/19/94
.\"	$Id: getgrent.3,v 1.1 1997/02/27 07:32:22 gdr Exp $
.\"
.TH GETGRENT 3 "27 January 1997" GNO "Library Routines"
.SH NAME
.BR getgrent ,
.BR getgrnam ,
.BR getgrgid ,
.BR setgroupent ,
.BR setgrent ,
.BR endgrent
\- group database operations
.SH SYNOPSIS
#include <sys/types.h>
.br
#include <grp.h>
.sp 1
struct group *
\fBgetgrent\fR (void);
.br
struct group *
\fBgetgrnam\fR (const char *\fIname\fR);
.br
struct group *
\fBgetgrgid\fR (gid_t \fIgid\fR);
.br
int
\fBsetgroupent\fR (int \fIstayopen\fR);
.br
int
\fBsetgrent\fR (void);
.br
void
\fBendgrent\fR (void);
.SH DESCRIPTION
These functions operate on the group database file
.BR /etc/group
which is described
in
.BR group (5).
Each line of the database is defined by the structure
.BR group
found in the include
file <grp.h>:
.nf

struct group {
	char	*gr_name;	/* group name */
	char	*gr_passwd;	/* group password */
	gid_t	gr_gid;		/* group id */
	char	**gr_mem;	/* group members */
};

.fi
Applications should never read
.BR /etc/group
directly, as the implementation of the group database is subject
to change.
.LP
The functions
.BR getgrnam 
and
.BR getgrgid 
search the group database for the given group name pointed to by
.BR name
or the group id 
.BR gid ,
respectively, returning the first one encountered.  Identical group
names or group gids may result in undefined behavior.
.LP
The
.BR getgrent 
function
sequentially reads the group database and is intended for programs
that wish to step through the complete list of groups.
.LP
All three routines will open the group file for reading, if necessary.
.LP
The
.BR setgroupent 
function
opens the file, or rewinds it if it is already open.  If
.I stayopen
is non-zero, file descriptors are left open, significantly speeding
functions subsequent calls.  This functionality is unnecessary for
.BR 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.
.LP
The
.BR setgrent 
function
is identical to
.BR setgroupent 
with an argument of zero.
.LP
The
.BR endgrent 
function
closes any open files.
.SH YP/NIS INTERACTION
When the
.BR yp (4)
group database is enabled, the
.BR getgrnam 
and
.BR getgrgid 
functions use the YP maps
.BR group.byname
and
.BR group.bygid ,
respectively, if the requested group is not found in the local
.BR /etc/group
file.  The
.BR getgrent 
function will step through the YP map
.BR group.byname
if the entire map is enabled as described in
.BR group (5).
.SH RETURN VALUES
The functions
.BR getgrent ,
.BR getgrnam ,
and
.BR 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 functions
.BR setgroupent 
and
.BR setgrent 
return the value 1 if successful, otherwise the value
0 is returned.
The functions
.BR endgrent 
and
.BR setgrfile 
have no return value.
.SH FILES
.IP \fB/etc/group\fR
group database file
.SH SEE ALSO
.BR getpwent 3 ,
.BR group 5 ,
.BR yp 4
.SH HISTORY
The functions
.BR endgrent ,
.BR getgrent ,
.BR getgrnam ,
.BR getgrgid ,
and
.BR setgrent 
appeared in v7.
The functions
.BR setgrfile 
and
.BR setgroupent 
appeared in 4.3BSD (Reno).
.SH COMPATIBILITY
The historic function
.BR setgrfile ,
which allowed the specification of alternate password databases, has
been deprecated and is no longer available.
.SH BUGS
The functions
.BR getgrent ,
.BR getgrnam ,
.BR getgrgid ,
.BR setgroupent 
and
.BR 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.
.LP
GNO does not currently make use of the 
.BR yp (4)
database.