I have a log file which contains a bunch of non visible control characters such as hex \u0003.
I would like to replace this using something like SED, but can't get the first part of the regex to match:
/s/^E/some_string
I am creating the ^E by pressing CTRL-V CTRL-0 CTRL-3 to create the special character, as read from the 'man ascii' page:
003 3 03 ETX
However, nothing matches this control character.
Any help appreciated!
You can also use the tr command. For example:
To delete the control character:
tr -d '\033' < file
To replace the control character with another:
tr '\033' 'x' < file
If you are not sure what the value of the control character is, perform an octal dump and it will print it out:
$ cat file
hello
^[
world
$ od -b file
0000000 150 145 154 154 157 012 033 012 167 157 162 154 144 012
0000016
So the value of control character ^[ is \033.
This perl one-liner will do the job - beware, it will modify the file:
perl -i -pe 's#\x{0003}#some_string#g' /path/to/log/file
If you want to replace a number of characters with character codes between a specified range:
echo {A..Z} | perl -i -pe 's#[\x{0040}-\x{0047}]#P#g'
P P P P P P P H I J K L M N O P Q R S T U V W X Y Z
(echo {A..Z} produces a string of alphabetic characters in bash)
-i to use perl as a filter.
This will replace all non-printable characters with a #
sed 's/[^[:print:]]/#/g' logfile
I'm not sure if I understand what you want, but if it is to substitute for occurrences of the successive hex bytes 0x00 0x03, this should work:
$ echo '0 61 20 00 03 0A' | xxd -r | sed 's/\x00\x03/test/g'
a test
^E(whatCtrl+0 Ctrl+3do depend on your terminal emulator and keyboard layout). Character 3 would beCtrl+V Ctrl+C.