Paths and Files - 10.15 Extracting a Path from a Full Path and Filename
(Page 2 of 4 )
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
See Also
Recipes 10.13 and 10.14
Next: 10.16 Replacing a File Extension >>
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 This article is excerpted from chapter 10 of the C++ Cookbook, written by Ryan Stephens, Christopher Diggins, Jonathan Turkanis and Jeff Cogswell (O'Reilly; ISBN: 0596007612). Check it out today at your favorite bookstore. Buy this book now.
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