Question

I have the following: param="/var/tmp/test"
I need to replace the word test with another word such as new_test

need a smart way to replace the last word after “/” with sed

Answer 1

Extracting bits and pieces with sed is a bit messy (as Jim Lewis says, use basename and dirname if you can) but at least you don’t need a plethora of backslashes to do it if you are going the sed route since you can use the fact that the delimiter character is selectable (I like to use ! when / is too awkward, but it’s arbitrary):

$ echo 'param="/var/tmp/test"' | sed ' s!/[^/"]*"!/new_test"! '
param="/var/tmp/new_test"

We can also extract just the part that was substituted, though this is easier with two substitutions in the sed control script:

$ echo 'param="/var/tmp/test"' | sed ' s!.*/!! ; s/"$// '
test