Perl

The perl -e gates

one-line looping

To download a book (this example is a free DSP book):

perl -e 'for ($i=1; $i<=19; $i++) { system "wget http://www.spectrumsdi.com/ch$i.pdf"; };'
perl -e 'for ($i=20; $i<=33; $i++) { system "wget http://www.innerlighttheory.com/ch$i.pdf"; };'