Ubuntu – How to remove square brackets, any text inside, and space after & before the brackets

Your problem with the regular expression is its greediness (the * and + quantifiers try to match as much, as they can). Unfortunately there is no way to tell sed to use non-greedy regular expressions. You have to use Perl to accomplish that, although ugly workarounds for sed do exist.

So try the following Perl one-liner:

perl -pe 's/\(.*?\)(, )?//g' /var/log/apt-history.log

That should manipulate the text as you wish. You will find PCRE (Perl regular expressions) very similar to the POSIX / GNU BRE and ERE one sed uses.

There's a lot of choice using the command line:

$ echo "2015-03-02 21:34:15      20480 dump-2015-03-02-21-34.tar" | cut -c32-
dump-2015-03-02-21-34.tar

$ echo "2015-03-02 21:34:15      20480 dump-2015-03-02-21-34.tar" | sed 's/.* //'
dump-2015-03-02-21-34.tar

$ echo "2015-03-02 21:34:15      20480 dump-2015-03-02-21-34.tar" | grep -oP "\S+$"
dump-2015-03-02-21-34.tar

$ echo "2015-03-02 21:34:15      20480 dump-2015-03-02-21-34.tar" | awk {'print $NF'}
dump-2015-03-02-21-34.tar

$ echo "2015-03-02 21:34:15      20480 dump-2015-03-02-21-34.tar" | perl -pe 's/.* //'
dump-2015-03-02-21-34.tar

$ echo "2015-03-02 21:34:15      20480 dump-2015-03-02-21-34.tar" | rev | cut -d ' ' -f 1 | rev
dump-2015-03-02-21-34.tar