File:
O000000667520994000000074720121112000000N^@^@^@
I used the below command but it doesn't work.
grep "^@^@^@" *
You can grep for any characters including control/non-printable characters in perl-regexp mode (-P) by its hex code:
grep -Pa '\x00' ...
grep -Pv '\x00' file
does not work in Cygwin...
-a
(sometimes?) it doesn't even find the pattern. Thanks! Might help @pbies as well.
Nov 21, 2019 at 8:10
^@
is not a carat ^
and at-sign @
, it's one character. It's how some programs display the NUL character—ASCII value 0, also known as \0
in C.
Here I've created a file with a NUL byte in it.† Notice that I use cat -v
to show non-printing characters.
$ cat -v blah
hello
null^@
hi
$ hexdump -C blah
00000000 68 65 6c 6c 6f 0a 6e 75 6c 6c 00 0a 68 69 0a |hello.null..hi.|
0000000f
Grep has trouble finding NULs since they're used to terminate strings in C. Sed, however, can do the job:
$ sed -n '/\x0/p' blah
null
$ sed -n '/\x0/p' blah | cat -v
null^@
† In vi, in insert mode press Ctrl-V, Ctrl-Shift-@ to insert a null byte.
/
to start searching and then Ctrl-V
, Ctrl-Shift-@
to insert a null byte, and then ENTER
. Then use N
ext and P
revious to show found instances.
May 25, 2022 at 13:36
If grep -P
doesn't work (e.g. on OS X), try this:
grep -E '\x00' ...
In bash you can add special characters when prefixed with C-q
or C-v
. So you can, for example
grep 'Ctrl-vCtrl-a' file.txt
The search string should be read as control key
+ character v
, followed by control key
+ character a
, which searches for ASCII value SOH (01). Unfortunately this doesn't work for the NUL character.
Character ^@ is the NUL char, so I'm afraid that it cannot be grepped directly.
Your best option would be probably to write a simple program that searches for this sequence of bytes.
Alternatively you may try to convert it into some form of hexadecimal dump (od
, xxd
or so) and grep into the output of it. But frankly speaking, it would be tricky to get it right.