How to read output of sed into a variable

Question

I have variable which has value \"abcd.txt\".

I want to store everything before the \".txt\" in a second variable, replacing the \".t

Answer 1

The simplest way is

logfile="${a/\.txt/\.log}"

If it should be allowed that the filename in $a has more than one occurrence of .txt in it, use the following solution. Its more safe. It only changes the last occurrence of .txt

logfile="${a%%\.txt}.log"