[root@devel3 bayes_cache]# uname -a
Linux devel3.blah.org 2.4.18-3smp #1 SMP Thu Apr 18 07:27:31 EDT 2002 i686 unknown
[root@devel3 bayes_cache]# man passwd
PASSWD(1)     User utilities      PASSWD(1)

NAME
       passwd - update a user's authentication tokens(s)

SYNOPSIS
       passwd [-k] [-l] [-u [-f]] [-d] [-S] [username]

DESCRIPTION
       Passwd is used to update a user's authentication token(s).
[snip]

       --stdin
              This option is used to indicate that passwd should read the new password 
              from standard  input,  which  can  be  a pipe.