跨平台方式获取用户友好的文件类型描述

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 closest that I think you can get out of Qt is QFileInfo .

Windows keeps track of the mapping through the registry that can be accessed through Qt's QSettings . But just from brief research it sounds like it might be kind tricky to mimic Explorer's mapping.

You can also launch the file with the default handler using QDesktopServices::openUrl() .

I haven't researched how or where OSX keeps track of the file type description information.

Hope that helps.

Answer 2

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