Ubuntu – How to remove lines from the text file containing specific words through terminal

command linetext processing

How to remove all the lines from the text file containing the words "cat" and "rat"?

Best Answer

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)

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