grep is a Unix command-line tool to search in files using regular expression.
In NetHack, most of the useful source is in src/*.c and include/*.h, thus you can grep the sources like this:
$ cd /path/to/nethack-3.4.3 $ grep -n regular-expression */*.{c,h}
Here is an example of searching for "Drow" in an unbuilt copy of the SLASH'EM sources:
$ cd /path/to/slashem-0.0.7E7F2 $ grep -n Drow */*.{c,h} src/u_init.c:1343: /* Drows can recognize all droven objects */ src/uhitm.c:40:/* Used to control whether Drow's sleep attack should succeed. */ include/you.h:356: /* KMH -- Drow is now its own role... */
It is sometimes useful to use grep to search for in-game messages. Want to know what a "wrenching sensation" is? Try this...
$ cd /path/to/nethack-3.4.3 $ grep -n 'wrenching sensation' */*.{c,h} src/sit.c:248: You_feel("a wrenching sensation."); src/spell.c:116: You_feel("a wrenching sensation."); src/teleport.c:847: You_feel("a wrenching sensation."); src/teleport.c:869: You_feel("a wrenching sensation.");
It can sometimes be difficult to find something successfully with grep. For example, a grep on 'You feel a wrenching sensation'
fails because NetHack uses the You_feel
function for those messages.
Sometimes, the use of printf-style formatting also impedes your search. For example, suppose that you get the message "You feel that eating the little dog was a bad idea.". You grep for it but get no results:
$ grep -n 'eating the little dog' */*.{c,h} $
You suspect that the monster is variable. You try again, searching for "bad idea" somewhere in the same line after "eating":
$ grep -n 'eating.*bad idea' */*.{c,h} src/eat.c:486: You_feel("that eating the %s was a bad idea.", mons[pm].mname); $
A look around eat.c#line486 (in vanilla 3.4.3) shows the following:
switch(pm) { case PM_LITTLE_DOG: case PM_DOG: case PM_LARGE_DOG: case PM_KITTEN: case PM_HOUSECAT: case PM_LARGE_CAT: if (!CANNIBAL_ALLOWED()) { You_feel("that eating the %s was a bad idea.", mons[pm].mname); HAggravate_monster |= FROMOUTSIDE; } break;
From this, you guess that message means that you now have the intrinsic of aggravate monster, and that eating a little dog, dog, large dog, kitten, housecat, or large cat causes it.
If you need to find in what file a certain function is defined, you can grep for the function name, prefixed with a caret, for example:
$ grep ^delobj *.c invent.c:delobj(obj) $