Answer: For executing any commands user uses a program known as the shell. Linux shell is basically a user interface used for executing the commands and communicating with Linux operating system. Shell does not use the kernel to execute certain programs, create files, etc.

There are several shells available with Linux which includes the following:

  • BASH (Bourne Again SHell)
  • CSH ( C Shell)
  • KSH ( Korn Shell)
  • TCSH

There are basically two types of Shell commands

  • Built-in shell commands: These commands are called from the shell and executed directly within the shell. Examples: 'pwd', 'help', 'type', 'set', etc.
  • External/ Linux commands: These commands are totally shell independent, have their own binary and are located in the file system.
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