case sensitivityenvironment-variablesgrep
I have set GREP_OPTIONS="--ignore-case --color" in ~/.bashrc as I normally want grep to work case-insensitive. However, there are times when I need grep to actually search case-sensitive, but the man page doesn´t suggest a param for this.
How can I achieve this?
I'm not sure how to enable this from the command line but when you're inside of less you can toggle the behavior you want by giving the -i command to less.
toggling -i
searching for /blah and /BLAH
searching for /Blah
Apparently you can also summon this mode on demand by suffixing your searches with a -i.
less prompt> /search string/-i
Assuming GNU grep (the default on Linux) you could use PCRE mode and negative lookbehinds:
$ grep -niP '(?<!de)bug|(?<!other)stuff|error' dummy.log
3:!bug
6:12345 DEBUG bug occured
7:please report BUG to me
8:the filename is critical_bug.log
9:bug should be fix.
11:throws error
12:a stuff
14:c otherstuff stuff
The options used are:
-n, --line-number
Prefix each line of output with the 1-based line number within
its input file.
-i, --ignore-case
Ignore case distinctions in patterns and input data, so that
characters that differ only in case match each other.
-P, --perl-regexp
Interpret PATTERNS as Perl-compatible regular expressions (PCREs).
This option is experimental when combined with the -z (--null-data)
option, and grep -P may warn of unimplemented features.
The magic happens in the lookbehind. The general format is (?!<foo)bar and this means "match bar but only if it isn't preceded by foo". So (?<!de)bug will match bug unless it comes after de and (?<!other)stuff will match stuff unless it comes after other.
Best Answer
I probably would define an alias with my options, e.g.:
as this would only affect interactive programs and not scripts. You could then just run
\grepor/bin/grepto run it without any options.If you want to keep using
GREP_OPTIONSyou can just unset it for your commandline, e.g.