Ubuntu – How to remove domain part of each line from text file containing email addresses

grep approach

To create a copy of the file without lines matching "cat" or "rat", one can use grep in reverse (-v) and with the whole-word option (-w).

grep -vwE "(cat|rat)" sourcefile > destinationfile

The whole-word option makes sure it won't match cats or grateful for example. Output redirection of your shell is used (>) to write it to a new file. We need the -E option to enable the extended regular expressions for the (one|other) syntax.

sed approach

Alternatively, to remove the lines in-place one can use sed -i:

sed -i "/\b\(cat\|rat\)\b/d" filename

The \b sets word boundaries and the d operation deletes the line matching the expression between the forward slashes. cat and rat are both being matched by the (one|other) syntax we apparently need to escape with backslashes.

Tip: use sed without the -i operator to test the output of the command before overwriting the file.

(Based on Sed - Delete a line containing a specific string)

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