#!/usr/bin/perl -w
## Demonstration of chatting with a bash shell.
use strict;
use IPC::Run qw( start pump finish timeout );
$IPC::Run::debug = 10;
my ( $in, $out );
die "usage: runsu <user> <password>" unless @ARGV;
my $user = @ARGV > 1 ? shift : $ENV{USER} || $ENV{USERNAME};
my $passwd = shift;
my $h = start(
    [ qw(su - ), $user ], '<pty<', \$in, '>pty>', \$out,
    timeout(5),
);
pump $h until $out =~ /^password/im;
$in = "$passwd\n";
## Assume atomic prompt writes
## and that a non-word is the last char in the prompt.
$out = '';
pump $h until $out =~ /([^\r\n\w]\s*)(?!\n)$/;
my $prompt = $1;
print "Detected prompt string = '$prompt'\n";
$prompt = quotemeta $prompt;
for (qw( ls ps fOoBaR pwd )) {
    $in  = $_ . "\n";
    $out = '';
    $h->timeout(5);    # restart the timeout
    pump $h until $out =~ s/\A((?s:.*))(?=^.*?$prompt(?!\n)\Z)//m;
    print map { "su: $_\n" } split( /\n/m, $1 );
}
$in = "exit\n";
finish $h ;