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# 1  
Old 01-01-2008
ksh if block question

Hi,

I am looking at a script, and it contains lines like:

Code:
if [[ $(echo $* | egrep -c 'DG') -eq 0 ]]
...

This is getting me confused. Why do we need $ before (echo $* | egrep -c 'DG')? Why can't we simply have:

Code:
if [[ (echo $* | egrep -c 'DG') -eq 0 ]]
...

i.e. no $ here before the ()...

Thanks.

J
# 2  
Old 01-01-2008
Hi.

Do you get the same result when you omit the "$"? ... cheers, drl
# 3  
Old 01-01-2008
Quote:
....Why can't we simply have:

if [[ (echo $* | egrep -c 'DG') -eq 0 ]]
Because the shell won't do command execution within the if condition, it will error out:

conditional binary operator expected

The condition expects an integer within itself, that's why you need the command substitution structure $( ) , where now the shell is told to execute the command within the braces:

Quote:
if [[ $(echo $* | egrep -c 'DG') -eq 0 ]]
or similarly:

Quote:
if [[ `echo $* | egrep -c 'DG'` -eq 0 ]]
# 4  
Old 01-01-2008
Excellent. Now it is clear.

Thanks.

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