Why doesn't grep ignore binary files by default?

Question

The manpage for grep describes the -I flag as follows:

-I      Ignore binary files.  This option is equivalent to 
        --binary-file=without-match option.

It also says this about binary files:

 --binary-files=value Controls searching and printing of binary files.
         Options are binary, the default: search binary files but do not print
         them; without-match: do not search binary files; and text: treat all
         files as text.

I cannot think of a scenario where I would care about matches in binary files. If such a scenario exists, surely it must be the exception rather than the norm. Why doesn't grep ignore binary files by default rather than requiring setting this flag to do so?

You can set the variable GREP_OPTIONS to your preferred settings, then you don't have to use that many command line switches. — Marco, Mar 28 '13 at 16:02
A note for other commands that do not support such a variable: You can set default options by defining an alias in your .(ba|z|foo)shrc':alias grep="grep -I"`. — Nova, Mar 28 '13 at 19:19
This can actually be very useful. For example, I was searching for the unity version of a project, and couldn't remember which file it was kept in. I searched for the format of the version, and it came up with some binary files that matches. It turned out as it was pre-version 5, the version was only present in a binary file, so without the binary match, I might have missed it. — Svend Hansen, Feb 02 '16 at 09:17
FYI There's a tool ack which is kind of "better than grep". Ack doesn't search binary files. In Debian, it comes under the name "ack-grep". — teika kazura, Feb 16 '17 at 06:12

score 107 · Accepted Answer · answered Mar 28 '13 at 15:59

107

Not everything that grep thinks is a binary file, is actually a binary file. e.g. puppet's logs have ansi color coding in them, which makes grep think they're binary. I'd still want to search them if I'm grepping through /var/log though.

answered Mar 28 '13 at 15:59

Dennis Kaarsemaker

8,530

5

The same goes for PDF files as well. – Joseph R. Mar 28 '13 at 17:45
15
historically grep could NOT do that, so for compatibility only, default have to be all-inclusive.

Olivier Dulac

Mar 28 '13 at 18:54

2

@OlivierDulac it makes sense, otherwise ignoring binary files should be the default. – Dagang Nov 25 '13 at 09:46

score 11 · Answer 2 · edited Jun 09 '15 at 12:00

11

grep’s ability to search binary files is also useful when I’m compiling a program and the linker (ld) complains about some function not being found. I can use a command like

grep function_name /lib/lib*

to find the library which contains it. (Libraries are binary files.)

edited Jun 09 '15 at 12:00

G-Man Says 'Reinstate Monica'

22,870

answered Jun 09 '15 at 11:38

Daniel Frużyński

281

In that case, you'd rather use grep -l function_name /lib/lib* or nm -Do /lib/lib* | grep function_name or ldconfig -p | grep -o '/.*/lib.*' | xargs nm -Do | grep function_name though. – Stéphane Chazelas Jun 09 '15 at 12:11
Well, grep some_function /lib/* is shorter and usually gives correct answer - name of library I am looking for. But yes, sometimes more sophisticated approach like your ones is required too. – Daniel Frużyński Jun 09 '15 at 12:42

score 2 · Answer 3 · edited Apr 05 '21 at 09:37

2

To process a binary file or a file that grep thinks is a binary file, use

grep --binary-files=text "data" f1 f2

edited Apr 05 '21 at 09:37

chaos

48,171

answered Apr 04 '21 at 15:39

user465055

31

This doesn't answer the question of why the behaviour is like it is, nor is even useful in the context where one says they "cannot think of a scenario where I would care about matches in binary files". Note that the opposite, ignoring binary files, which is actually useful in that context was already mentioned in the question. – ilkkachu Apr 04 '21 at 16:25

Why doesn't grep ignore binary files by default?

3 Answers3