Question

I’m trying to escape characters within backticks in my bash command, mainly to handle spaces in filenames which cause my command to fail.

The command I have so far is:

grep -Li badword `grep -lr goodword *`

This command should result in a list of files that do not contain the word “badword” but do contain “goodword”.

Answer 1

Your approach, even if you get the escaping right, will run into problems when the number of files output by the goodword grep reaches the limits on command-line length. It is better to pipe the output of the first grep onto a second grep, like this

grep -lr -- goodword * | xargs grep -Li -- badword

This will correctly handle files with spaces in them, but it will fail if a file name has a newline in it. At least GNU grep and xargs support separating the file names with NUL bytes, like this

grep -lrZ -- goodword * | xargs -0 grep -Li -- badword

EDIT: Added double dashes -- to grep invocations to avoid the case when some file names start with - and would be interpreted by grep as additional options.