Executables

You're familiar with the idea of reading and writing data into files. But what about executing them? Executable files are just files where the data stored inside is a program that you can run on your computer.

Files with a .sh extension are shell scripts. They're just text files that contain shell commands. You can run a file in your shell by typing its filepath:

mydir/program.sh

Interestingly, if the program is in the current directory (in this example, the mydir directory), you need to prefix it with ./ to run it:

./program.sh

As far as file paths go, ./program.sh and program.sh are the same. The dot (.) is an alias for the current directory. We need the prefix when running executables so that the shell knows we're trying to run a file from a file path, not an installed command like ls, mkdir, chmod, etc.