for loop in bash simply prints n times the command instead of reiterating

Question

I have a input.txt file with over 6000 lines.

If a line a has over 10 words then I want it to be split but not at the 10th word but where the first comma character appe

Answer 1

I think I see what you're after. There are a few problems with your approach:

• awk doesn't process files in-place. So your sub() makes a change, 1 prints to stdout, but your input file never changes.
• When you sub(), you don't insert a new record into the input stream that awk is processing. Your command merely adds a newline to the current record.

Given these, you could get away with processing the input multiple times, as you've suggested. But rather than arbitrarily assuming that you'll have a maximum of seven 10-word phrases on a line, it might be better to actually detect whether you need to continue. Something like this:

#!/usr/bin/env bash

input=input.txt
temp=$(mktemp ${input}.XXXX)
trap "rm -f $temp" 0

while awk '
  BEGIN { retval=1 }
  NF >= 10 && /, / {
    sub(/, /, ","ORS)
    retval=0
  }
  1
  END { exit retval }
' "$input" > "$temp"; do
  mv -v $temp $input
done

This uses an exit value from awk to determine whether we need to run another iteration of the bash loop. If awk detects that no substitutions were required, then the loop stops.