Shell Scripts Variables Test

Hi_This_is_Dev · 08-05-2010, 08:49 AM

What will be the output of the following Shell Script?

Code:

a="1245"

[-n $a]
echo $?

[-z $a]
echo $?

That was asked in the interview I attended today.

centosboy · 08-05-2010, 09:07 AM

Quote:

Originally Posted by Hi_This_is_Dev

What will be the output of the following Shell Script?

Code:

a="1245"

[-n $a]
echo $?

[-z $a]
echo $?

That was asked in the interview I attended today.

and did you get it correct??
$a = 12345

so

test if variable is a not empty

-n $a
echo $? returns 0

test if variable is zero bytes
-z $a
echo $? returns 1

not too hard..

Hi_This_is_Dev · 08-05-2010, 09:18 AM

Quote:

Originally Posted by centosboy

and did you get it correct??
$a = 12345

so

test if variable is a not empty

-n $a
echo $? returns 0

test if variable is zero bytes
-z $a
echo $? returns 1

not too hard..

I also mentioned the same answer:

0
1

But the numbers were in quotation marks. Besides, the $ was missing. That also confused me.

centosboy · 08-05-2010, 09:34 AM

Quote:

Originally Posted by Hi_This_is_Dev

I also mentioned the same answer:

0
1

But the numbers were in quotation marks. Besides, the $ was missing. That also confused me.

what do you mean $ was missing???
i have actually written it incorrectly

$a=value - wrong
a=value - correct

ghostdog74 · 08-05-2010, 10:28 AM

Quote:

Originally Posted by Hi_This_is_Dev

I also mentioned the same answer:

0
1

But the numbers were in quotation marks. Besides, the $ was missing. That also confused me.

wrong, both will give you error. must have spaces between square brackets.

Hi_This_is_Dev · 08-28-2010, 08:21 PM

Quote:

Originally Posted by ghostdog74

wrong, both will give you error. must have spaces between square brackets.

Well, friend, PHP uses $ before variable name so I forgot that $ is not used in Shell Script when we assign a value to a variable.

About a single space after [ and before ], all I can say is that they often print incorrectly on papers and it is not sure whether to test us or it is their typo.

Code:

a="1245"

[-n $a]
echo $?

Above, even though we know that a single space after [ and before ] is required there but they would ask us to choose an option from:

[A] 0
[B] 1
[C] 5
[D] 7

and we know no output is going to be generated as the statement is incorrect.

Sometimes, in exams / test or interview it becomes a problem to figure out if they really meant it or forgot to review it.