Why is sed not recognizing \t as a tab?

Question

sed \"s/\\(.*\\)/\\t\\1/\" $filename > $sedTmpFile && mv $sedTmpFile $filename

I am expecting this sed script to insert a <

Answer 1

Use $(echo '\t'). You'll need quotes around the pattern.

Eg. To remove a tab:

sed "s/$(echo '\t')//"