How to replace specific string in a text file with empty space

As a glob, *.tar.gz means any string ending with .tar.gz. Sed, however, does not use globs, it uses regular expressions and regular expressions have a different syntax. Try:

sed -i -e 's//[^/]*.tar.gz//g' copyright

In the above, the regex / matches anything that starts with / (because / is being used as the sed divider, we escape it as /) followed by [^/]* which matches zero or more of any character except /, followed by .tar.gz where the . are escaped so that they match only periods. (In normal regex notation, . matches any one character.)

There are many difference between globs (as used by the shell) and regular expressions (which are used by sed, grep, and other important tools). In a glob, . means a period. In regex, . is a wildcard meaning any single character. In a glob, * means zero or more of any character. In a regex, * means zero of more of the preceding thing.

Advanced topic

We don't have to use / as the divider in a sed substitute command. Other dividers are possible such as @:

sed -i -e 's@/[^/]*.tar.gz@@g' copyright

Because in the above, we use @ as the dividor instead of /, we have no need to escape the first /.