regexgrepregex-negation

Negated character not working with literal `]`

I have a file test.txtwhich contains

ERROR [x]

If I try

grep -Eo "ERROR \[[^p]\]" test.txt

it matches ERROR [x].

But if I do:

grep -Eo "ERROR \[[^\]]\]" test.txt

which is trying to match ERROR [ followed by any character expect literal ], it does not match.

It should, since x is not a ].

What am I missing ?

Solution

  • You don't need to escape the ] string in the match group. The correct expression is the following:

    ERROR \[[^]]\]

    Test:

    echo "ERROR []]" | grep -Eo "ERROR \[[^]]\]" # no match

echo "ERROR [x]" | grep -Eo "ERROR \[[^]]\]" # match

echo "ERROR [a]" | grep -Eo "ERROR \[[^]]\]" # match

echo "ERROR [abcdef]" | grep -Eo "ERROR \[[^]]\]" # no match

    Tested on macOS 15.5.