path: root/lib/libc/gen/getpwent.3

.\"	$OpenBSD: getpwent.3,v 1.18 2003/05/30 14:00:32 jmc Exp $
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.Dd December 11, 1993
.Dt GETPWENT 3
.Os
.Sh NAME
.Nm getpwent ,
.Nm getpwnam ,
.Nm getpwuid ,
.Nm setpassent ,
.Nm setpwent ,
.Nm endpwent
.Nd password database operations
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <pwd.h>
.Ft struct passwd *
.Fn getpwent void
.Ft struct passwd *
.Fn getpwnam "const char *login"
.Ft struct passwd *
.Fn getpwuid "uid_t uid"
.Ft int
.Fn setpassent "int stayopen"
.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 functions
.Fn getpwnam
and
.Fn getpwuid
search the password database for the given login name or user ID,
respectively, always returning the first one encountered.
.Pp
.Fn getpwent
sequentially reads the password database and is intended for programs
that wish to process the complete list of users.
.Pp
.Fn setpassent
accomplishes two purposes.
First, it causes
.Fn getpwent
to
.Dq rewind
to the beginning of the database.
Additionally, if
.Fa stayopen
is non-zero, file descriptors are left open, significantly speeding
up subsequent accesses for all of the routines.
(This latter functionality is unnecessary for
.Fn getpwent
as it doesn't close its file descriptors by default.)
.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open as the database will become out of date if it is updated while the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.
.Pp
.Fn setpwent
is equivalent to
.Fn setpassent
with an argument of zero.
.Pp
The
.Fn endpwent
function closes any open files.
.Pp
These routines have been written to
.Dq shadow
the password file, e.g.,
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 RETURN VALUES
The functions
.Fn getpwent ,
.Fn getpwnam ,
and
.Fn getpwuid
return a valid pointer to a passwd structure on success
or a null pointer if end-of-file is reached or an error occurs.
The
.Fn setpassent
function returns 0 on failure or 1 on success.
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 pw_dup 3 ,
.Xr passwd 5 ,
.Xr pwd_mkdb 8 ,
.Xr vipw 8
.Sh HISTORY
The
.Fn getpwent ,
.Fn getpwnam ,
.Fn getpwuid ,
.Fn setpwent ,
and
.Fn endpwent
functions appeared in
.At v7 .
The
.Fn setpassent
function appeared in
.Bx 4.3 Reno .
.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 functions
.Fn getpwent ,
.Fn getpwnam ,
and
.Fn getpwuid
leave their results in an internal static object and return
a pointer to that object.
Subsequent calls to any of these functions will modify the same object.
.Pp
The routines
.Fn getpwent ,
.Fn endpwent ,
.Fn setpassent ,
and
.Fn setpwent
are fairly useless in a networked environment and should be
avoided, if possible.