Question

What’s a cross-platform way for getting a user-friendly description of a file?

Examples:

1. foo.pdf -> “Portable Document Format (PDF)
2. bar.doc -> “Microsoft Word Document”

Pointers to libraries or appropriate system APIs would be highly appreciated.

A Qt/C++ solution is preferred but anything is fine.

Target platforms are Windows and Mac OS X. I’d prefer the descriptions to match what would be found in Explorer or Finder if possible (rather than maintaining a map of extensions -> descriptions myself).

Answer 1

The GNU File command is builtin for Linux and OSX, and there is a version available for Windows (http://gnuwin32.sourceforge.net/packages/file.htm).

File tests each argument in an attempt to classify it. There are three
sets of tests, performed in this order: filesystem tests, magic number
tests, and language tests. The first test that succeeds causes the
file type to be printed. The type printed will usually contain one of
the words text (the file contains only printing characters and a few
common control characters and is probably safe to read on an ASCII
terminal), executable (the file contains the result of compiling a
program in a form understandable to some UNIX kernel or another), or
data meaning anything else (data is usually `binary’ or
non-printable). Exceptions are well-known file formats (core files,
tar archives) that are known to contain binary data.

You could invoke the file command using QProcess and display the returned info.

Output looks like :

$ file document.pdf
document.pdf: PDF document, version 1.5
$ file test.txt
test.txt: ASCII text, with CRLF, CR, LF line terminators