curl is an amazing tool to perform HTTP calls.
Some less known features of it are:
URL templates
curl accepts a certain level of “templating” in its URLs:
curl https://www.google.com/search?q={a,b}&t=[1-10]Will generate the following (sequential) HTTP calls:
https://www.google.com/search?q=a&t=1
https://www.google.com/search?q=a&t=2
https://www.google.com/search?q=a&t=3
https://www.google.com/search?q=a&t=4
https://www.google.com/search?q=a&t=5
https://www.google.com/search?q=a&t=6
https://www.google.com/search?q=a&t=7
https://www.google.com/search?q=a&t=8
https://www.google.com/search?q=a&t=9
https://www.google.com/search?q=a&t=10
https://www.google.com/search?q=b&t=1
https://www.google.com/search?q=b&t=2
https://www.google.com/search?q=b&t=3
https://www.google.com/search?q=b&t=4
https://www.google.com/search?q=b&t=5
https://www.google.com/search?q=b&t=6
https://www.google.com/search?q=b&t=7
https://www.google.com/search?q=b&t=8
https://www.google.com/search?q=b&t=9
https://www.google.com/search?q=b&t=10However, these will be sequential and executed one at a time. If we wanted to parallelize them, we can make use of the -P parameter (that will allow multiple connections), but curl needs to be called through xargs.
Different options for multiple calls
curl accepts multiple URLs to perform requests:
curl https://www.google.com/search?q=a https://www.google.com/search?q=bHowever, the same options will apply for each of them. If we wanted to change them, we can use the -: or --next option:
curl https://www.google.com/search?q=a -: -X 'POST' https://www.google.com/search?q=b