Shell script

1. ' and " are different in bash. String delimited with ' are literal strings and will not substitute variable values whereas " delimited string will.

2. List of special variables to refer to arguments.

   • $0: name of the script

   • $1 to $9: arguments to the scripts

   • $@: all the arguments

   • $#: number of arguments

   • $?: return code of the previous command

   • !!: entire last command

   • $_: last argument from the last command

3. $(CMD) will execute CMD and get the outut of the command and subsitute it in place