The autopasswd script included with tcl/tk doesn't work at all because it
sends the password before passwd starts listening for a password.  This
results in the script just hanging.

Even if it did work, certain passwords (eg. those beginning with a hyphen)
cannot be set because the password is interpreted as an option to "send".

The replacement script below fixes both of the above problems.  I don't
know if the 0.1s sleep is sufficient in all cases, but I've not had it fail
for me yet.

#!/usr/bin/expect --
# wrapper to make passwd(1) be non-interactive
# username is passed as 1st arg, passwd as 2nd

set password [lindex $argv 1]
spawn passwd [lindex $argv 0]
expect "password:"
sleep 0.1
send -- "$password\r"
expect "password:"
sleep 0.1
send -- "$password\r"
expect eof