OpenBSD-4.6/lib/libc/gen/getpwent.3

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.\"	$OpenBSD: getpwent.3,v 1.24 2009/06/01 21:52:03 millert Exp $
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.Dd $Mdocdate: June 1 2009 $
.Dt GETPWENT 3
.Os
.Sh NAME
.Nm getpwent ,
.Nm setpwent ,
.Nm endpwent
.Nd sequential password database access
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <pwd.h>
.Ft struct passwd *
.Fn getpwent void
.Ft void
.Fn setpwent void
.Ft void
.Fn endpwent void
.Sh DESCRIPTION
These functions operate on the password database file which is described in
.Xr passwd 5 .
Each entry in the database is defined by the structure
.Li struct passwd
found in the include file
.Aq Pa pwd.h :
.Bd -literal -offset indent
struct passwd {
	char	*pw_name;	/* user name */
	char	*pw_passwd;	/* encrypted password */
	uid_t	pw_uid;		/* user uid */
	gid_t	pw_gid;		/* user gid */
	time_t	pw_change;	/* password change time */
	char	*pw_class;	/* user access class */
	char	*pw_gecos;	/* Honeywell login info */
	char	*pw_dir;	/* home directory */
	char	*pw_shell;	/* default shell */
	time_t	pw_expire;	/* account expiration */
};
.Ed
.Pp
The
.Fn getpwent
function sequentially reads the password database and is intended for programs
that wish to process the complete list of users.
.Pp
It is dangerous for long-running programs to keep the file descriptors
open as the database will become out of date if it is updated while the
program is running.
Furthermore, programs that run child processes should be careful to call
.Fn endpwent
to close these descriptors before calling
.Xr execve 2
or
.Xr system 3 .
.Pp
.Fn setpwent
causes
.Fn getpwent
to
.Dq rewind
to the beginning of the database.
.Pp
The
.Fn endpwent
function closes any file descriptors opened by
.Fn setpwent
or
.Fn getpwent .
.Pp
These routines have been written to
.Dq shadow
the password file, that is,
allow only certain programs to have access to the encrypted password.
If the process which calls them has an effective UID of 0 or has the
.Dq _shadow
group in its group vector, the encrypted password will be returned, otherwise,
the password field of the returned structure will point to the string
.Ql * .
.Sh YP SUPPORT
If YP is active,
.Fn getpwent
also uses the
.Pa master.passwd.byname
YP map (if available) or the
.Pa passwd.byname
YP map.
This is in addition to the passwd file,
and respects the order of both normal and YP
entries in the passwd file.
.Sh RETURN VALUES
The
.Fn getpwent
function returns a valid pointer to a passwd structure on success
or a null pointer if end-of-file is reached or an error occurs.
.Pp
The
.Fn endpwent
and
.Fn setpwent
functions have no return value.
.Sh FILES
.Bl -tag -width /etc/master.passwd -compact
.It Pa /etc/pwd.db
insecure password database file
.It Pa /etc/spwd.db
secure password database file
.It Pa /etc/master.passwd
current password file
.It Pa /etc/passwd
a Version 7 format password file
.El
.Sh SEE ALSO
.Xr getlogin 2 ,
.Xr getgrent 3 ,
.Xr getgrouplist 3 ,
.Xr getpwnam 3 ,
.Xr pw_dup 3 ,
.Xr passwd 5 ,
.Xr Makefile.yp 8 ,
.Xr pwd_mkdb 8 ,
.Xr vipw 8 ,
.Xr yp 8
.Sh HISTORY
The
.Fn getpwent ,
.Fn setpwent ,
and
.Fn endpwent
functions appeared in
.At v7 .
.Pp
The historic function
.Xr setpwfile 3 ,
which allowed the specification of alternate password databases,
has been deprecated and is no longer available.
.Sh BUGS
The
.Fn getpwent
function stores its results in an internal static buffer and returns
a pointer to that buffer.
Subsequent calls to
.Fn getpwent ,
.Fn getpwnam ,
or
.Fn getpwuid
will overwrite the same buffer.
.Pp
The routines
.Fn getpwent ,
.Fn endpwent ,
and
.Fn setpwent
are fairly useless in a networked environment and should be
avoided, if possible.