Grep hex characters in a file

Question

I am having some difficulty finding the number of hex characters in a file. For example:

grep -o \x02 file | wc -l
0

There should be about 3M matches here, but it doesn't seem like the \x02 character is being recognized here. For example (in python):

>>> s=open('file').read()
>>> s.count('\x02')
2932267

see https://stackoverflow.com/a/17168847/10622916 or https://stackoverflow.com/a/23757973/10622916 — Bodo, Jan 23 '19 at 09:27

score 0 · Answer 1 · answered Jan 23 '19 at 16:19

0

This seems to do what you want on macOS:

printf "\x02\n3\n\x02" | grep -c "\x02"
2

answered Jan 23 '19 at 16:19

Mark Setchell

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score 0 · Accepted Answer · answered Jan 24 '19 at 12:57

The answer by Mark Setchell may be OK for MacOS but doesn't seem to work on debian using bash (tested with bash 4.4, grep 2.27).

I could get a match using the -P directive (for Perl regex)

user@host:~ $ printf '\x02\n3\n\x02' | grep -c -P '\x02'
2
user@host:~ $ printf '\x02\n3\n\x02' | grep -c -P '\xFF' #same input, different pattern
0
user@host:~ $ printf '\x02\n3\n\xff' | grep -c -P '\xFF' #match with unmatching case
2

Hope this helps

Grep hex characters in a file

2 Answers2