Differentiate between ELFves and scripts quickly

Question

How do I use file to differentiate between ELFves and scripts as quickly as possible?

I don't need any further details, just ELF, script (/plaintext), or other/error.

Answer 1

If it's just between ELF and script, you may not need file at all. With bash:

IFS= LC_ALL=C read -rn4 -d '' x < file case $x in ($'\x7fELF') echo ELF;; ("#!"*) echo script;; (*) echo other;; esac 

(-d '' (to use NUL character as delimiter) is to work around the fact that bash's read otherwise just ignores the NUL bytes in the input).

See also:

• Searching for 32-bit ELF file
• Fastest way to determine if shebang is present

Answer 2

Create a custom magic(5) file that contains only the tests you need.

The stock elf test can be fetched from https://github.com/file/file/blob/master/magic/Magdir/elf , and then cut down even further. text is built-in, so you don't need to include it.

To avoid the parsing it each time, put it in its own directory and compile it to mgc:

file -C -m dir 

This will output dir.mgc. (Specifying -m dir/ will instead output .mgc.) Then it will be used by subsequent runs:

file -m dir 

Answer 3

Turns out I can exclude the following tests to speed it up:

encoding tokens cdf compress elf tar 

(Tests are excluded with -e $test_name).

It looks like I need the ascii and the soft test.