To make grep find all occurrences of the word QEMU with case variations except for the exact cases QEMU, qemu, and Qemu, you can use a negative lookahead in a Perl-compatible regular expression (PCRE).

Command:

bash
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grep -P '(?i:QEMU)(?!\b(QEMU|qemu|Qemu)\b)' /path/to/file

Explanation:

1. (?i:QEMU): Enables case-insensitive matching for the term QEMU.
2. (?!\b(QEMU|qemu|Qemu)\b): Ensures that the matched term is not exactly QEMU, qemu, or Qemu (using word boundaries \b to avoid partial matches).

Example:

If you want to search in a file named example.txt, run:

bash
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grep -P '(?i:QEMU)(?!\b(QEMU|qemu|Qemu)\b)' example.txt

Notes:

• The -P flag enables PCRE (Perl-compatible regular expressions) in grep. Ensure your grep version supports it (GNU grep does).
• If -P is not available, use egrep or grep -E with a more complex pattern, but PCRE is the cleanest solution here.

Would you like help testing this on a sample file?