C++: How to check if a file/directory is readable? (PHP equivalent: is_readable)

Question

I am trying to validate a directory with C++.

http://php.net/manual/en/function.is-readable.php

bool is_readable ( string $filename )
Tells whether a file (or directroy) exists and is readable.

What would be the equivalent of the above in C++?

I am already using the boost/filesystem library to check that the directory exists. I have checked the documentation:
http://www.boost.org/doc/libs/1_44_0/libs/filesystem/v3/doc/index.htm
but I cannot find the equivalent of PHP's is_readable().

If it is not possible with the boost/filesystem library, what method would you use?

Answer 1

Most operating systems provide stat().

Answer 2

1. Since you've tagged the question "Linux", there is a POSIX function to check if the file is readable/writable/executable by the user of the current process. See man 2 access.

   int access(const char *pathname, int mode);
   

   For example,

   if (-1 == access("/file", R_OK))
   {
       perror("/file is not readable");
   }
   

2. Alternatively, if you need portability, try to actually open the file for reading (e.g. std::ifstream). If it succeeds, the file is readable. Likewise, for directories, use boost::filesystem::directory_iterator, if it succeeds, directory is readable.