Is there a way to detect null bytes (␀, NUL, \0) in sed?

Question

Related to another question, in order to fuzzily detect binary files, is there a way to detect ␀ bytes in sed?

In GNU sed, yes, but note that on many unices, text utilities are not capable of handling null bytes. — Gilles 'SO- stop being evil'
– Gilles 'SO- stop being evil', Commented Apr 19, 2012 at 1:04

jippie · Accepted Answer · 2012-04-18 09:43:21Z

24

Example:

Prove I'm sending a NUL byte, followed by a newline:

$ echo -e \\0 | hexdump -C
00000000  00 0a                                             |..|
00000002

Now I change the NUL byte to an ! exclamation mark:

$ echo -e \\0 | sed 's/\x00/!/' | hexdump -C
00000000  21 0a                                             |!.|

So the trick is using \x00 as NUL-byte.

answered Apr 18, 2012 at 9:43

jippie

14.6k10 gold badges49 silver badges67 bronze badges

jofel · Accepted Answer · 2012-04-18 12:05:14Z

10

Yes, the pattern \x00 matches to the null byte.

Example:

$ printf "\0\n\0\n" > file
$ sed -e 's/\x00/test/' -i file
$ cat file
test
test
$

answered Apr 18, 2012 at 9:34

jofel

27.4k8 gold badges71 silver badges97 bronze badges

2 Answers 2