Know Your Environment

Kernel ?

• An intermediate program
• Interface between hardware & software

Shell?

• An interface between users & Kernel/OS
• cat /etc/shells : check which all shell programs are available in your OS
• echo $0 : check your current shell
• cat /etc/passwd : check which user is associated with which shell

Shell Types ?

• Graphical Shells
  • Gnome
  • KDE
• CLI Shells
  • sh (bourne shell)
  • bash (bourne again shell)
  • csh & tcsh
  • ksh (korn shell - solaris)

Shell Scripting ?

• Put all instructions in a specific file & RUN it on Shell
• Give file extension as .sh (not mandatory)

Run a Shell Script ?

• Absolute path (example - /home/student/scripts/testing.sh)
• Reletive path (example - ./testing.sh, when you are already present at /home/student/scripts/ directory)

Scripting Best Practices

• Script File Convention :
  • make a work directory & keep scripts in it.
  • script name should identify function/operation
  • extension can be given as .bash/.csh/.ksh if working in multiple shells.
• Script File Permission :
  • chmod a+x name (make executable)
• Shell Script Format :
  • Define Shell (#!/bin/bash)
  • Comments (# comments)
  • Define Variables
  • Commands
  • Statements (include indentation)
• Script is executed from top to bottom in sequence.
• Add Exit/Status Code in your code :
  • If code is 0 : Code executed successfully
  • Else if code is 1-255 : Code execution was not successful.