What makes grep consider a file to be binary?

Question

I have some database dumps from a Windows system on my box. They are text files. I'm using cygwin to grep through them. These appear to be plain text files; I open them with text editors such as notepad and wordpad and they look legible. However, when I run grep on them, it will say binary file foo.txt matches.

I have noticed that the files contain some ascii NUL characters, which I believe are artifacts from the database dump.

So what makes grep consider these files to be binary? The NUL character? Is there a flag on the filesystem? What do I need to change to get grep to show me the line matches?

Answer 1

If there is a NUL character anywhere in the file, grep will consider it as a binary file.

There might a workaround like this cat file | tr -d '\000' | yourgrep to eliminate all null first, and then to search through file.

Answer 2

You can use the strings utility to extract the text content from any file and then pipe it through grep, like this: strings file | grep pattern.

Answer 3

The file /etc/magic or /usr/share/misc/magic has a list of sequences that the command 'file' uses for determining the file type. Note that binary may be just a fallback solution. Sometimes files with strange encoding are considered binary too.

grep on Linux has some options to handle binary files like --binary-files or -U / --binary