By default awk and sed do not expand shell or system variables and do not pass their own variables back to the shell. To use shell variables awk and sed statements must be included in double-quotes. Here are a few examples:

1) You have a file (words.txt) containing a list of words and their replacements as shown below.

Shell

blue red yellow green stormy blue dark clear

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blue red yellow green stormy blue dark clear

You also have a text file (text.txt) where you need to replace the words from the list above with the corresponding alternatives.

Shell

blue flowers were growing on a yellow lawn under a dark stormy sky

1	blue flowers were growing on a yellow lawn under a dark stormy sky

Here’s a shell script to do it:

Shell

#!/bin/ksh cat words.txt | while read LINE do O=$(echo "$LINE" | awk '{print $1}') R=$(echo "$LINE" | awk '{print $2}') cat text.txt | sed "s/$O/$R/g" > tmp.txt mv tmp.txt text.txt done

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#!/bin/ksh cat words.txt | while read LINE do      O=$(echo "$LINE" | awk '{print $1}')      R=$(echo "$LINE" | awk '{print $2}')        cat text.txt | sed "s/$O/$R/g" > tmp.txt      mv tmp.txt text.txt done

The resulting text.txt file would read:

Shell

red flowers were growing on a green lawn under a clear blue sky

1	red flowers were growing on a green lawn under a clear blue sky