Replace a string in shell script using a variable

Question

I am using the below code for replacing a string inside a shell script.

echo $LINE | sed -e \'s/12345678/\"$replace\"/g\'

but it\'s getting

Answer 1

To let your shell expand the variable, you need to use double-quotes like

sed -i "s#12345678#$replace#g" file.txt

This will break if $replace contain special sed characters (#, \). But you can preprocess $replace to quote them:

replace_quoted=$(printf '%s' "$replace" | sed 's/[#\]/\\\0/g')
sed -i "s#12345678#$replace_quoted#g" file.txt