how to change file content in text file

Question

this is test.txt

hello mate
good morning
no worries

and this is my code

#!/bin/bash

while
do
printf "whice one do you change? "
read change
printf "how to change? "
read after
done < test.txt

I want to change "good" to "gooood" in test.txt file

and here is conditions
-not using sed
-not using perl

How can I change it? please give me a hand~!!!

Answer 1

sed is the best tool for this simple replacement but if not allowed to use tools, you can revert back to bash functionality

 while read line; do echo ${line/good/goood}; done < good.txt > goood.txt

assuming the original file is good.txt, this will replace the string "good" to "goood" and write to goood.txt.

Answer 2

awk '{ sub(/good/, "goood"); print }' test.txt > tempfile && mv tempfile test.txt

或者您可以使用awk进行就地修改：

awk -i inplace '{ sub(/good/, "goood"); print }' test.txt