Script

Commands

Command	Function
#!/bin/bash or #!/bin/sh	shebang
VAR=var	set VAR to var
$VAR	inserts var whereever $VAR is placed
case - esac	inserts case
if [ “var” == “var” ]; then fi	inserts if

Operator	Description
-eq	Returns true if two numbers are equivalent
-lt	Returns true if a number is less than another number
-gt	Returns true if a number is greater than another number
==	Returns true if two strings are equivalent
!=	Returns true if two strings are not equivalent
!	Returns true if the expression is false
-d	Check the existence of a directory
-e	Check the existence of a file
-r	Check the existence of a file and read permission
-w	Check the existence of a file and write permission
-x	Check the existence of a file and execute permission
-z	string is null, that is, has zero length
-n	string is not null.

Running your script prompts interpreter error

Open your script with vi and execute the following

 :set fileformat=unix

Running your script requires more rights

Make your script executable with the following command

chmod +x [scriptname].sh