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Using awk in a for loop

 
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# 1  
Old 05-01-2013
Using awk in a for loop
Hi,

I have a for loop using awk where I add a column to each file data1.txt through data10.txt where the value in the new column equals 1 through 10:

Code:
for i in {1..10}; do awk '$3="$i"' data$i.txt > output$i.txt; done

But when I run the code, i just get a bunch of $i's in the third column. How can I modify the code? Thanks
# 2  
Old 05-01-2013
If I understand what you are trying to do, try this:
Code:
for i in {1..10}; do awk '{$3=i; print}' i=$i data$i.txt > output$i.txt; done

This User Gave Thanks to hanson44 For This Post:
evelibertine
# 3  
Old 05-01-2013
I doubt what you need is a comparison == not assignment =:
Code:
awk '{$3=i}'
awk '{$3==i}'

Anyway awk is an overkill for this task. You can achieve this using a bash script:
Code:
#!/bin/bash

for i in {1..10}
do
        while read a b c skip
        do
                [ $c -eq $i ] && echo "$a $b $c $skip" >> output${i}.txt
        done < data${i}.txt
done

---------- Post updated at 17:02 ---------- Previous update was at 16:49 ----------

By the way if it is assignment that you need, just modify the code to:
Code:
#!/bin/bash

for i in {1..10}
do
        while read a b c skip
        do
                c=$i; echo "$a $b $c $skip" >> output${i}.txt
        done < data${i}.txt
done

# 4  
Old 05-02-2013
The shell code would misbehave if field3 is not a number or field1 begins with a -
A correction like
Code:
[ "$c" = "$i" ] &&

sees 01 not equal to 1 ...
How much easier is
Code:
awk '$3==i'

Without { } of course.
 
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