C++ Cookbook

10.15. Extracting a Path from a Full Path and Filename

Problem

You have the full path of a filename, e.g., d:\apps\src\foo.c, and you need to get the pathname, d:\apps\src.

Solution

Use the same technique as the previous two recipes by invoking rfind and substr to find and get what you want from the full pathname. See Example 10-23 for a short sample program.

Example 10-23. Get the path from a full path and filename

#include <iostream>
#include <string>

using std::string;

string getPathName(const string& s) {

   char sep = '/';

#ifdef _WIN32
   sep = '\\';
#endif

   size_t i = s.rfind(sep, s.length());
   if (i != string::npos) {
      return(s.substr(0, i));
   }

   return("");
}

int main(int argc, char** argv) {

   string path = argv[1];

   std::cout << "The path name is \"" << getPathName(path) << "\"\n";
}

Discussion

Example 10-23 is trivial, especially if you’ve already looked at the previous few recipes, so there is no more to explain. However, as with many of the other recipes, the Boost Filesystem library provides a way to extract everything but the last part of the filename with its branch_path function. Example 10-24 shows how to use it.

Example 10-24. Getting the base path

#include <iostream> #include <cstdlib> #include <boost/filesystem/operations.hpp> using namespace std; using namespace boost::filesystem; int main(int argc, char** argv) { // Parameter checking... try { path p = complete(path(argv[1], native)); cout << p.branch_path().string() << endl; } catch (exception& e) { cerr << e.what() << endl; } ...