Somewhat depending on what you consider to be a C file, that is a highly non-trivial task! I don't think the compiler test would satisfy me because it would generate too many false negatives and maybe even some false positives. I've written plenty of files that I would consider C (or C++) files, but which a compiler would fail to compile, either because of missing header files or because of syntax errors.

In like fashion probing the file for interesting common character sequences is likely to be rather error prone.

What is your friend's use case? Often if you focus just on solving the problem for the use case you can simplify the solution and end up with something that is robust for the task at hand. For example just matching files that have a .c extension may be sufficient and is very easy, fast to implement and very fast executing.

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.