How to use regexp to perform a glob in C/C++ (Linux)

Question

I need to match simple some simple glob patterns that include only * and ?. It occurred to me that I could transform the input pattern into a regexp - the only problem is I'm not familiar with regexp enough to know the replacements.

Essentially, I need an implementation for:

std::string getRexExpForGlob(const std::string& globPattern);

Note these matches aren't used for anything to do with the filesystem, so POSIX glob won't do.

Answer 1

* in a glob pattern is equivalent to .* in regex. ? is equivalent to . . In most regex dialects, . does not match a newline by default, and so if you need it to match that character, check your library for how to set that flag.

Answer 2

Depending on your OS, you may have <fnmatch> with int fnmatch(const char* pattern, const char* string, int flags) . This allows glob patterns against arbitrary strings, and a few extra flags to allow flexibility beyond that needed for filename matching.

Otherwise, glob's * and ? are equivalent to regexp .* and . respectively. (Globs can also have [] alternatives but you've said yours don't).

Answer 3

In regular expressions, . represents any single character. This maps to ? in glob patterns. Similarly, .* represents any sequence of characters, which maps to * in glob patterns. You should be able to write a workable function from that.