Demonstration by Example This was originally answered by me at Quora #!/bin/sh sleep 50 let’s save it as a.sh and make it executable sudo chmod +x a.sh Let’s run it in the background and stat the process. ./a.sh& [1] 11660 On looking at the process details: ps -fp 11660 UID PID PPID C STIME TTY TIME CMD sudipbh+ 11660 11330 0 15:30 pts/7 00:00:00 /bin/sh ./a.sh We can see that the content of the file is passed as an argument to the program /bin/sh.

Working with multiple versions Most of the times we as developers are working on multiple version of the language or the framework. If not managed properly it can be a nightmare dealing with different projects which use different versions of the same language. Say, project A uses python2 and project B uses python3. In python we have virtual environments which can be managed using, among many others, pipenv. Likewise for Ruby we have rbenv.