使用Shell脚本将$ a $替换为＆a

Question

I want to replace all the occurrences of $[az|AZ|0-9]$ to &[az|AZ|0-9] using shell script. For example, $HELLO$ should become &HELLO .

I/P - $HELLO$
o/P - &HELLO

I tried using sed to replace the string.

sed -i -e 's/$*$/&/g filename

I/P - $HELLO$
O/P - &HELLO&

But I am unable to make sure that the last $ is replaced by a blank space and not &

Answer 1

Using grouping and backreference::

$ sed 's/\$\([a-zA-Z0-9]*\)\$/\&\1/g' <<< '$HELLO$'
&HELLO

Answer 2

Solution using awk : This uses awk's inbuilt function sub to search and replace $ sign and then sub is again used to replace $ to & .

echo '$HELLO$' |awk '{sub(/\$/,"\\&");sub(/\$/,"")}1'
&HELLO