C++ Cookbook

10.17. Combining Two Paths into a Single Path

Problem

You have two paths and you have to combine them into a single path. You may have something like /usr/home/ryan as a first path, and utils/compilers as the second, and wish to get /usr/home/ryan/utils/compilers, without having to worry whether or not the first path ends with a path separator.

Solution

Treat the paths as strings and use the append operator, operator+=, to compose a full path out of partial paths. See Example 10-26.

Example 10-26. Combining paths

#include <iostream>
#include <string>

using std::string;

string pathAppend(const string& p1, const string& p2) {

   char sep = '/';
   string tmp = p1;

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

  if (p1[p1.length()] != sep) { // Need to add a
     tmp += sep;                // path separator
     return(tmp + p2);
  }
  else
     return(p1 + p2);
}

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

   string path = argv[1];

   std::cout << "Appending somedir\\anotherdir is \""
             << pathAppend(path, "somedir\\anotherdir") << "\"\n";
}

Discussion

The code in Example 10-26 uses strings that represent paths, but there’s no additional checking on the path class for validity and the paths used are only as portable as the values they contain. If, for example, these paths are retrieved from the user, you don’t know if they’re using the right OS-specific format, or if they contain illegal characters.

For many other recipes in this chapter I have included examples that use the Boost Filesystem library, and when working with paths, this approach has lots of benefits. ...