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What is the meaning of "-s" option in "if" statement?

 
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# 1  
Old 05-03-2012
What is the meaning of "-s" option in "if" statement?
Hi Guys,

I'm sorry but I can't find answer for this, what is the meaning of -s option in "if" statement on unix scipting. Please see sample below:

Code:
opath=/home/output

for i in N1 N2 N3 N4
do
echo $i
if [ -s $opath/$i.GRAI ] 
then
grep $i $opath/N5_CRAI > $opath/N5_$i.crai
chmod 777 $opath/N5_$i.crai


Please advise Smilie

BR,
rymnd_12345
# 2  
Old 05-03-2012
read man test

Code:
 -s file       True if file exists and has a size greater than zero.

# 3  
Old 05-03-2012
Thanks DukeNuke2!
# 4  
Old 05-03-2012
For the entire list of options, see the man page for your shell.

Code:
man bash

Search for conditional expressions.

---------- Post updated at 08:45 AM ---------- Previous update was at 08:42 AM ----------

Oops, I didn't see DukeNuke2's comment about man test. That's easier to use than the huge man page for the shell. Smilie
# 5  
Old 05-03-2012
... and it's not a Conditional Expression . In the syntax posted it is a Test .

There is some overlap in the syntax for a Conditional Expression and a Test but they are not interchangeable.
# 6  
Old 05-03-2012
man test is not particularly intuitive as the test command isn't explicitly used in the if [ -s $opath/$i.GRAI ] expression.

On some Unix implementations, you can just run man [
Last edited by jlliagre; 05-03-2012 at 11:03 AM..
# 7  
Old 05-03-2012
The bash man page says it is a conditional expression:

Quote:
Conditional expressions are used by the [[ compound command and the test and [ builtin commands
My original point, however, is that the "-letter" syntax is easier to lookup in the man test page than it is in the man bash page.
 
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