grepping binary files and UTF16

Question

Standard grep/pcregrep etc. can conveniently be used with binary files for ASCII or UTF8 data - is there a simple way to make them try UTF16 too (preferably simultaneously, but instead will do)?

Data I'm trying to get is all ASCII anyway (references in libraries etc.), it just doesn't get found as sometimes there's 00 between any two characters, and sometimes there isn't.

I don't see any way to get it done semantically, but these 00s should do the trick, except I cannot easily use them on command line.

Answer 1

The easiest way is to just convert the text file to utf-8 and pipe that to grep:

iconv -f utf-16 -t utf-8 file.txt | grep query

I tried to do the opposite (convert my query to utf-16) but it seems as though grep doesn't like that. I think it might have to do with endianness, but I'm not sure.

It seems as though grep will convert a query that is utf-16 to utf-8/ascii. Here is what I tried:

grep `echo -n query | iconv -f utf-8 -t utf-16 | sed 's/..//'` test.txt

If test.txt is a utf-16 file this won't work, but it does work if test.txt is ascii. I can only conclude that grep is converting my query to ascii.

EDIT: Here's a really really crazy one that kind of works but doesn't give you very much useful info:

hexdump -e '/1 "%02x"' test.txt | grep -P `echo -n Test | iconv -f utf-8 -t utf-16 | sed 's/..//' | hexdump -e '/1 "%02x"'`

How does it work? Well it converts your file to hex (without any extra formatting that hexdump usually applies). It pipes that into grep. Grep is using a query that is constructed by echoing your query (without a newline) into iconv which converts it to utf-16. This is then piped into sed to remove the BOM (the first two bytes of a utf-16 file used to determine endianness). This is then piped into hexdump so that the query and the input are the same.

Unfortunately I think this will end up printing out the ENTIRE file if there is a single match. Also this won't work if the utf-16 in your binary file is stored in a different endianness than your machine.

EDIT2: Got it!!!!

grep -P `echo -n "Test" | iconv -f utf-8 -t utf-16 | sed 's/..//' | hexdump -e '/1 "x%02x"' | sed 's/x/\\\\x/g'` test.txt

This searches for the hex version of the string Test (in utf-16) in the file test.txt