CODEWITHSUNDEEP
linuxshell
Leonardo
Leonardo

Reputation: 131

What is the use of space in shell?

I have a shell program as follow:

#!/bin/sh
a=1
b=2
c=`expr $a+$b`      
echo $c

The output is 1+2.

But if I change

c=`expr $a+$b\`

to

c=`expr $a + $b`

The output is going to be 3.

I wonder what is the use of space here.

Upvotes: 0

Views: 145

Answers (1)

tom
tom

Reputation: 19163

expr is a shell command expecting arguments of two types: operands (the "numbers") and operators (+, -, *, etc.). In your case, you want to pass three arguments to expr, which are $a, +, and $b. The dollar sign values are expanded into their actual values of 1 and 2 by your shell, and not by expr. So, when you do expr $a + $b, the actual shell command is expr 1 + 2, which gives you 3.

When you don't put spaces in, what gets executed is expr 1+2. The expr program doesn't know what to do with 1+2 as its sole argument, and thus just echoes it back untouched.

Upvotes: 2

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