You have to source [wiki:roelkluin/cvars cvars] to use these tools and run these commands in your git Linux kernel directory.

gg

gg does something like

git grep -n -E [other_options] "$(bli2 "$1")"

bli2

bli2() parses a string and transforms it into a more complex extended regexp, which it simply echoes.

To understand how it parses things try these:

bli2 "@V"
bli2 "@d"
bli2 " "
bli2 "
 "

Note that @V will catch the identifier of a simple local variable, @d will catch a number (even if it's a hex or 1ull), spaces are squeezed and parsed to match optional spaces.

bli2 pattern	echoed (description)	echoed literal	number of backrefs
any space	optional space	:space:*	no backref
\!	exclamation mark (because bash otherwise bangs)	!	no backref
@S	obligatory space	:space:+	no backref
@V	identifier	[[:alpha:]_]+[[:alnum:]_]*	no backref
@K	identifier in only uppercases	[[:upper:]_]+[[:upper:][:digit:]_]*	no backref
@Q	a non-alnumeric	[^[:alnum:]_]	no backref
@Q2	a non-alnumeric or extension to the left of a variable	[^[:alnum:]_>.]	no backref
@w	(pointer) member, array	see `bli2 "@w"'	one backref
@d	any number	see `bli2 "@d"'	one backref
\(...\)	up to 2 nested parentheses	see `bli2 "\(...\)"'	two backrefs
\{...\}	up to 2 nested curly brackets	see `bli2 "\{...\}"'	two backrefs
\[...\]	up to 2 nested square brackets	see `bli2 "\[...\]"'	two backrefs
\(-..\)	characters optionally followed by up to 2 nested parentheses	see `bli2 "\(...\)"'	three backrefs
\{-..\}	characters optionally followed by up to 2 curly brackets	see `bli2 "\{...\}"'	three backrefs
\{.8.\}	up to 8 curly brackets	see `bli2 "\(...\)"'	eight backrefs

gres

I wrote this to do a multiline (git-)grep

lets say we want to search for an erroneous pattern like this:

for (i = 0; i < n; i++) {}
...
if (i > n) ...

We can match this with:

gres -B1 -A40 "@V < @d ;" "for \( (@V) = @d ; \1 < (@d) ; \1 \+\+ \) \{.8.\}@n if \( \1 > \3 \)"

For me - I currently have kernel version 2.6.33-rc2 - this results after a few seconds in:

--
---[ vi drivers/mmc/host/s3cmci.c +1209 ]---
        /* Set clock */
        for (mci_psc = 0; mci_psc < 255; mci_psc++) {
                host->real_rate = host->clk_rate / (host->clk_div*(mci_psc+1));

                if (host->real_rate <= ios->clock)
                        break;
        }

        if (mci_psc > 255)
                mci_psc = 255;

        host->prescaler = mci_psc;
        writel(host->prescaler, host->base + S3C2410_SDIPRE);

        /* If requested clock is 0, real_rate will be 0, too */
        if (ios->clock == 0)
                host->real_rate = 0;

So how does it work? gres does something in the order of:

git grep -E -n -other_opts "$(bli2 "$1")" -- '*.c' '*.h' | sed -n -r "$(ecsed2 "${@:2})"

The -B1' and -A40' are passed to git-grep, bli2() parses the first pattern and subsequent patterns are passed to ecsed2().

ecsed2

ecsed2() parses the `git grep' output and prints only the ones of which the last passed pattern matches, prior patterns (if any) are excluded.