[vram22]

For people who would like to go further, and explore writing command line tools (instead of only using them), in C [1], for Linux [2], this post and the linked article in it, by me, may be of help:

Developing a Linux command-line utility:

http://jugad2.blogspot.in/2014/09/my-ibm-developerworks-arti...

[1] In C, but the utility development guidelines described in the article mostly apply to other languages like Python and Ruby too, since the main principles are the same.

[2] It may compile and run on Mac OS X too, since it is a Unix, but I haven't tested it on that platform.