Grep : How to grep for strings inside binary data

Grep or Global Regular Expression Print is a very useful Unix/Linux command that I've practically used everyday. So, recently a co-worker asked me how to grep for a piece of string inside binary data files ?

for example, there is a binary file

printf "\x01 text \x00\r\ntext\r\n\x02text text\r\n\x92" > data.bin

What he wanted is to grep for the 'text' string for the data.bin file

To do that, use the cat command with -v flag

From the cat man page:

-v Display non-printing characters so they are visible. Control characters print as ^X' for control-X; the delete character (octal 0177) prints as `^?.

Non-ASCII characters (with the high bit set) are printed as `M-' (for meta) followed by the character for the low 7 bits.

without the -v flag, the grep result will look something like this

cat data.bin | grep text

Binary file (standard input) matches

therefore, use cat -v before passing the result to grep

cat -v data.bin | grep text

^A text ^@^M

text^M

^Btext text^M

Hope this short tutorial on greping for strings inside binary data file can be useful to you.