How to Replace Names in Column of a Text File, Using a Conversion Present in Another Text File With Bash

Question

I did a search, and none of the other posts fit my situation. Basically, I have a long master text file that looks something like this:

Group1 0 100
Group2 100 200
Group3 200 300
Group4 300 400

Ect..

I need to replace the names in the master text file, using another text file that lists what they should be converted to. That conversion text file looks like this:

Group1 Team1
Group2 Team2
Group3 Team2
Group4 Team3

So by using a script, I want to convert the master text file as such:

Team1 0 100
Team2 100 200
Team2 200 300
Team3 300 400

Again, these are big files, and they are not the same lengths. Any help is MUCH appreciated!

Answer 1

Read the conversion list into an array, then use it to replace the first field in the original file:

awk 'NR == FNR { a[$1] = $2; next } { $1 = a[$1] } 1' conversion.txt original.txt

• NR == FNR condition targets the first file (total line number equals file line number)
• next skips the rest of the script and goes to the next line
• 1 is a condition that is always true, so do the default action, { print }

If you want to make sure that a replacement exists, you can add a condition $1 in a before the second action block.