$ zmodload zsh/zpty
  $ zpty PW passwd $1
  $ zpty PW passwd $1
# ``-r'': read the output of the command name.
# ``z'' : Parameter
  $ zpty -r PW z '*password:'
# send the to command name the given strings as input
  $ zpty -w PW $2
  $ zpty -r PW z '*password:'
  $ zpty -w PW $2
# The second form, with the -d option, is used to delete commands
# previously started, by supplying a list of their names. If no names
# are given, all commands are deleted. Deleting a command causes the HUP
# signal to be sent to the corresponding process.
  $ zpty -d PW