Hi tobyink,

thanks for your kind reply. You are right, I do need to send password to keyboard, not STDIN. I have tried code you suggested, but the linux still asks for the password. My code is as this:

#!/usr/bin/perl

open my $pipe,'|-', 'cvs update';
print {$pipe} "my_password\n";
close $pipe;
[download]

did I miss something? thanks.