Extracting a Path from a Full Path and Filename

Problem

You have the full path of a filename, e.g., d:appssrcfoo.c, and you need to get the pathname, d:appssrc.

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 
#include 

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) << ""
";
}

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 
#include 
#include 

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:srcccbc10>binGetPathBoost.exe c:windowssystem321033
c:/windows/system32