Parsing a curl json response and using response to build another request
On OS X you can use the system Perl:
curl -sS http://xkcd.com/info.0.json | /usr/bin/perl -pe 's/.*"num": ([0-9]+).*/\1/'You can save the output to a variable with command substitution:
num=$(curl -sS http://xkcd.com/info.0.json | /usr/bin/perl -pe 's/.*"num": ([0-9]+).*/\1/')curl -sS "http://xkcd.com/${num}/info.0.json"or more concisely, two-in-one, albeit not very readable:
curl -sS "http://xkcd.com/$(curl -sS http://xkcd.com/info.0.json | /usr/bin/perl -pe 's/.*"num": ([0-9]+).*/\1/')/info.0.json"
By the way, I highly recommend jq as the command line JSON processor. To extract num with jq, it's as simple as
curl -sS http://xkcd.com/info.0.json | jq '.num'and although you didn't ask for it, here's a simple one-liner with jq that extracts the URI of the latest image:
curl -sS "http://xkcd.com/$(curl -sS http://xkcd.com/info.0.json | jq '.num')/info.0.json" | jq -r '.img'Example output:
http://imgs.xkcd.com/comics/spice_girl.png