Usage:
On Linux, copy the provided magic file to ~/.magic.
$ cp magic $HOME/.magic
On macOS, use the -m option with the "file" command.
$ file -m path/to/magic <file(s)>
For other systems, consult the manual page for the "file" command.
Once magic file is installed, file command will recognize kdb files.
For example,
$ file taq/2014.07.09/quote/*
taq/2014.07.09/quote/asize: kdb+ data file version 3 int
taq/2014.07.09/quote/ask: kdb+ data file version 3 real
taq/2014.07.09/quote/bid: kdb+ data file version 3 real
taq/2014.07.09/quote/bsize: kdb+ data file version 3 int
taq/2014.07.09/quote/ex: kdb+ data file version 3 char
taq/2014.07.09/quote/mode: kdb+ data file version 3 char
taq/2014.07.09/quote/sym: kdb+ data file version 3 enum by sym partitioned
taq/2014.07.09/quote/time: kdb+ data file version 3 time