UNIX for Dummies Questions & Answers

i think this works with the premise.

If the awk version works, that will be much faster.

If it doesn't, please describe how. I've done the best I can with an incomplete description.

Sorry for the confusion. I can't figure out how to use you awk with the restriction of the while loop in my premise. The output file that I need to generate requires other information from other calculations. So extracting the mapped number at once will not work since I need to work on it line by line. Thanks

You can pipe awk into the entire loop.

Code:

awk ... | while read LINE
do
        echo $LINE
done

Hi Kokoro, I I understand you correctly then you need to find labels and values in the file mapping.txt, corresponding to the labels in the file input_strings and both files may be quite large. And subsequently you need this result in a while loop so that you can work with this in shell variables inside the loop. Give this a try:

Code:

grep -wFf input_string.txt mapping.txt |
while IFS="|" read -r label val
do
  echo "label $label has value $val"
done > outfile

The grep may have false matches if one of the values are equal to one of the labels.
An alternative to grep might be:

Code:

awk -F\| 'NR==FNR{A[$1];next}$1 in A' input_string.txt mapping.txt |

So you can feed either the grep or the awk into the loop and see which one works better.