Bash

Bash (short for Bourne Again SHell) is the main scripting language used to provide a command line to Linux. I covered it briefly in Linux 101, but I will be covering it more in depth here. Very rarely will you write entire programs in bash, but it is a quick way to do many tasks all in one if you master it, it's just a little confusing as most lower level languages tend to be at times.

The most basic thing with bash, is that there is a variable that sets what directories to look for executable files. Every time you run a command, it searches these folders for a matching file to execute. These files can be anything, from python scripts to bash scripts to compiled executable files.

Bash builtins

The following is a list of the most common built in commands in bash with examples:

• alias
  • alias dir=ls
  • Will create a special note that says "hey, if this command is executed, run this command instead." The example will basically say if the command dir is typed, run ls instead.
• echo
  • echo "bash"
  • echo "$PATH"
  • Prints out the text passed as an argument. Can be used in conjunction with variables to view them.
• cd
  • cd Desktop
  • Changes the working directory.
• export
  • export MYVAR="PASSME"
  • Sets variables to be passed to child processes of the shell itself.
• history
  • history
  • history -c
  • Shows history of commands ran, use -c to clear it.
• source
  • source .bashrc
  • Restarts the shell using the file specified as the file that contains all the options. By default this is a file in your home directory named ".bashrc" and sourcing it again will restart the shell if you add anything to the file (like aliases).
• pwd
  • prints the current directory.
• exit/logout
  • The logout command only works if you are not running a terminal in a Linux UI. This does exactly what it sounds like and logs you out. The exit command does the same, but it works regardless of if you are running a terminal in the UI or running Linux with just a command line.