sed replace string with environment variable code example

Example 1: replace using sed

#on my mac
sed -i -e 's/old-text/new-text/g' text.txt

Example 2: sed replace with variable

Just concatenate var '"$var"' to replace values string in sed command:
$ sed -i 's/string_to_replace/'"$var"'/g' file_to_replace.txt

Example 3: replace text with sed

sed -i 's/old-text/new-text/g' input.txt