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;
   }
  return(EXIT_SUCCESS);
}

Sample output from Example 10-24 looks like this:

D:\src\ccb\c10>bin\GetPathBoost.exe c:\windows\system32\1033
c:/windows/system32

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