How to write shell script

• Use any editor to write shell script.
• After writing shell script set execute permission for your script as follows:

  $ chmod +x your-script-name
  or
  $ chmod 755 your-script-name
  

• Execute your script as;

  $ bash your-script-name
  $ sh your-script-name
  $ ./your-script-name
  

• In the last syntax ./ means current directory.
• But only . (dot) means execute given command file in current shell without starting the new copy of shell as follows;

  $ . your-script-name
  

  Now you are ready to write first shell script that will print "Knowledge is Power" on screen. http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/firstfirst

  #
  # My first shell script
  #
  clear
  echo "Knowledge is Power"
  

  After saving the above script, you can run the script as follows:

  $ ./first
  

  This will not run script since we have not set execute permission for our script first; to do this type command

  $ chmod 755 first
  $ ./first
  

• Script to print user information who currently login , current date and time.http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/ginfoginfo

  #
  #Script to print user information who currently login , current date
  # & time
  #
  clear
  echo "Hello $USER"
  echo -e "Today is \c ";date
  echo -e "Number of user login : \c" ; who | wc -l
  echo "Calendar"
  cal
  exit 0
  

  At the end why statement exit 0 is used?