HOWTO remove null characters from a file

Sometimes files may be filled up with null characters that look like ^@ when you open them in a text editor. This may happen when a disk becomes full, or when you rename a logfile while an application is still writing to it.

I ran into this problem today, and I fixed it using a command called ‘tr’. This is a utility capable of translating or deleting characters from standard input/output. It means you can use it to ‘pipe’ input to it, and send the output to a new file. For example:

cat file.log | tr -d '\000'  > new_file.log 

Note: when using this in a script, you might need to escape that backslash.

What does this command do? Using the -d switch we delete a character. A backslash followed by three 0’s represents the null character. This just deletes these characters and writes the result to a new file. Problem solved!