68427

How to grep for presence of specific hex bytes in files?

Question:

My web app is displaying some bizarro output (unicode characters that shouldn't be there, etc.). The best I can reckon is that somehow I introduced a bad char somewhere in the source, but I can't figure out where.

I found <a href="https://stackoverflow.com/a/17168847" rel="nofollow">this answer</a> that states I can do something like:

grep -obUaP "<\x-hex pattern>" .

When I copy the unicode char out of the browser and into my <a href="http://home.gna.org/bless/" rel="nofollow">Bless</a> hex editor, it tells me that the exact bytes of the char are:

<blockquote>

15 03 01 EF BF BD 02 02

</blockquote>

How can I format <\xhex pattern> to match the exact bytes that I need. I tried:

grep -obUaP "<\x-15 03 01 EF BF BD 02 02>" .

But that doesn't work. Thoughts?

Answer1:

Check the post again. FrOsT is not including the '<' and '>' in his actual grep command. He only used the carats to enclose an example statement. His actual statement looks like this:

"\x01\x02"

not:

"<\x01\x02>"

I have a C source file on my computer that begins with the line:

#include <stdio.h>

When I run

grep -obUaP '\x69\x6E\x63\x6C\x75\x64\x65' io.c

I get

1:include

That is, the line number followed by <em>only</em> the string matching the pattern.

You may want to run

man grep

and find out what all those options mean.

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