I have following file, called for example "a.txt"
Now I want to replace each first character at a line followed by "_", by the same character followed by "@",
in other words I wish to receive following file.
It's important for me to execute the upper task using sed editor, and I do it in the following way:
>> sed s/"^(.)_"/"\0@"/ a.txt > b.txt
But for any reason this command doesn't work.
Can you please explain what is a problem.