ed is not working when looping through file- shell scriping

Question

#!/bin/bash
filename='urls.txt'
old_url="test"
while read line
do
  new_url=$line
  echo "New URL  is "$new_url
  echo -e '%s/'"$new_url"'/'"$old_url"'/g\nw' |ed ca-sample.conf
  old_url=$new_url
  echo ""
  echo "Old URL  is "$old_url
  sleep 60
done < $filename
exit

I am looping through urls.txt to read the lines one by one to replace the old url with the new one. This command (echo -e '%s/'"$new_url"'/'"$old_url"'/g\nw' |ed ca-sample.conf) is working fine in command line (I have set the new_url and old_url as env variables "export new_url="New" and "export old_url="Old") but when I put this command in While loop it is not working.

Answer 1

Repeatedly editing a file in a loop is horribly inefficient. You probably want something like

awk -v old_url="test" '{ print "s%" old_url "%" $0 "%g"; old_url = $0 }' urls.txt |
tac |
sed -i~ - ca-sample.conf

Your sed might not accept a script on standard input; maybe store the generated script in a temporary file and pass that instead of -.

I put in the tac so that the new URL will not immediately be replaced with a newer one still. Depending on what your data looks like and what you are actually trying to accomplish, this could be completely wrong, and/or require additional tweaks (regex anchors, for one thing?)

The verbose printing and the long sleep seem more distracting than helpful, though I suppose you could hack them back in if you really wanted to. Also pay attention to the quoting -- you are quoting literal text (which doesn't need quoting) and leaving variables outside quotes (which is precisely what should crucially be inside quotes, for the quotes to be useful at all).