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Old 10-27-2010, 09:57 PM   #1
cliffyao
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Registered: Oct 2009
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How to use awk in a for loop?


I just wrote a code as

Code:
for((i=1; i<=5; i++))
do
	awk '$1=="$i"' input.txt > output_$i\.txt
done
I want to take out the lines in the input.txt in which their first columns are 1 or 2 or 3 or 4 or 5, to get 5 output files as

output_1.txt
output_2.txt
output_3.txt
output_4.txt
output_5.txt

This code doesn't work unfortunately..

Anyone knows how to make it work?

Thanks in advance
 
Old 10-27-2010, 10:56 PM   #2
neonsignal
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You just have a minor quoting problem. Because you are using single quotes, the '$i' is not being expanded out by the shell. Modifying the awk line to this will help:
Code:
awk "\$1==$i" input.txt >output_$i.txt
(notice that the '$' in $1 is being escaped, so that the shell does not attempt to expand it)

Last edited by neonsignal; 10-27-2010 at 10:58 PM.
 
Old 10-27-2010, 11:51 PM   #3
grail
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Not exactly ... the issue is actually the $i means nothing inside awk. You either have to quote accordingly or use an awk variable.
I prefer the second as the quoting option gets very messy if you have to use it more than once:
Code:
awk -vtest=$i '$1 == test' input.txt > output_${i}.txt
 
  


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