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//usr/share/doc/perl-IPC-Run-0.84/eg/factorial_scalar
#!/usr/bin/perl -w ## Demonstration of using a scalar to queue input to a child process use strict ; use IPC::Run qw( start timeout ) ; die "usage: $0 <num>\n\nwhere <num> is a positive integer\n" unless @ARGV ; my $i = shift ; die "\$i must be > 0, not '$i'" unless $i =~ /^\d+$/ && $i > 0 ; my ( $in, $out ) ; my $h = start ['bc'], \$in, \$out, timeout( 5 ) ; $in = "a = i = $i ; i\n" ; while () { $out = '' ; $h->pump until $out =~ s/.*?(\d+)\n/$1/g ; print "bc said: $out\n" ; if ( $out > $i ) { print "result = $out\n" ; $in = undef ; last ; } elsif ( $out == '1' ) { ## End of calculation loop, get bc to output the result $in = "a\n" ; } else { $in = "i = i - 1 ; a = a * i ; i\n" ; } } $h->finish ;
