Web Technology Experts Notes

This indicates that the script should be run in the bash shell regardless of which interactive shell.

Question: What sign is used in unix for comment a line?
Pound Sign

Pound sign (#), is used to comment a line.

# echo "this is comment"

Question: When to use single quote OR Double quote?
Single quote: When you are assigning string without variable, then you should use single quote.
Double quote: When you are assigning string with variable, then you should use Double quote.

Question: What's wrong in following variable?

strVar = "Hello World! How are you?" 
echo $strVar;

There should not be space before and after the equal sign (=). Correct code are below:

strVar="Hello World! How are you?" 
echo $strVar;

Question: Give sample example of If else?

if condition1
then
 statement1
 statement2
 statement3
 
else
 statement4
 statement5
fi

Question: Give sample example of If elseif?

if condition1
then
 statement1
 statement2
 statement3
 
elif condition2
then
 statement4
 statement5
 
elif condition3
then
 statement6
 statement7
 statement8
fi

Question: Give list of Operator used in unix shell scripting?

Operator	Results	number of operands
-n	operand non zero length	1
-z	operand has zero length	1
-d	there exists a directory whose name is operand	1
-f	there exists a file whose name is operand	1
-eq	the operands are integers and they are equal	2
-neq	the opposite of -eq	2
=	the operands are equal (as strings)	2
!=	opposite of =	2
-lt	operand1 is strictly less than operand2 (both operands should be integers)	2
-gt	operand1 is strictly greater than operand2 (both operands should be integers)	2
-ge	operand1 is greater than or equal to operand2 (both operands should be integers)	2
-le	operand1 is less than or equal to operand2 (both operands should be integers)	2