Home arrow C++ arrow Directories in C++
C++

Directories in C++


In this fourth part of a five-part series that focuses on streams and files in C++, you will learn how to handle directories. 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). Copyright © 2007 O'Reilly Media, Inc. All rights reserved. Used with permission from the publisher. Available from booksellers or direct from O'Reilly Media.

Author Info:
By: O'Reilly Media
Rating: 5 stars5 stars5 stars5 stars5 stars / 12
November 06, 2008
TABLE OF CONTENTS:
  1. · Directories in C++
  2. · 10.11 Removing a Directory
  3. · 10.12 Reading the Contents of a Directory
  4. · 10.13 Extracting a File Extension from a String

print this article
SEARCH DEVARTICLES

Directories in C++
(Page 1 of 4 )

10.10 Creating a Directory

Problem

You have to create a directory, and you want to do it portably, i.e., without using OS-specific APIs.

Solution

On most platforms, you will be able to use the mkdir system call that is shipped with most compilers as part of the C headers. It takes on different forms in different OSs, but regardless, you can use it to create a new directory. There is no standard C++, portable way to create a directory. Check out Example 10-15 to see how.

Example 10-15. Creating a directory

#include <iostream>
#include <direct.h>

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

   if (argc < 2) {
      std::cerr << "Usage: " << argv[0] << " [new dir name]\n";
      return(EXIT_FAILURE);
  
}

   if (mkdir(argv[1]) == -1) { // Create the directory
      std::cerr << "Error: " << strerror(errno);
      return(EXIT_FAILURE);
  
}
}

Discussion

The system call for creating directories differs somewhat from one OS to another, but don't let that stop you from using it anyway. Variations of mkdir are supported on most systems, so creating a directory is just a matter of knowing which header to include and what the functionís signature looks like.

Example 10-15 works on Windows, but not Unix. On Windows, mkdir is declared in <direct.h>. It takes one parameter (the directory name), returns -1 if there is an error, and sets errno to the corresponding error number. You can get the implementation-defined error text by calling strerror or perror.

On Unix, mkdir is declared in <sys/stat.h>, and its signature is slightly different. The error semantics are just like Windows, but there is a second parameter that specifies the permissions to apply to the new directory. Instead, you must specify the permissions using the traditional chmod format (see the chmod man page for specifics), e.g., 0777 means owner, group, and others all have read, write, and execute permissions. Thus, you might call it like this on Unix:

  #include <iostream>
  #include <sys/types.h>
  #include <sys/stat.h>

  int main(int argc, char** argv) {

     if (argc < 2) {
        std::cerr << "Usage: " << argv[0] << " [new dir name]\n";
        return(EXIT_FAILURE);
    
}

     if (mkdir(argv[1], 0777) == -1) {  // Create the directory
        std::cerr << "Error: " << strerror(errno);
        return(EXIT_FAILURE);
    
}
  }

If you want portability, and don't want to write all the #ifdefs yourself, you should consider using the Boost Filesystem library. You can create a directory using the create_directory function, as shown in Example 10-16, which contains a short program that creates a directory.

Example 10-16. Creating a directory with Boost

#include <iostream>
#include <string>
#include <cstdlib>
#include <boost/filesystem/operations.hpp> #include <boost/filesystem/fstream.hpp>

using namespace std;
using namespace boost::filesystem;

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

   // Parameter checking...
  
try {
     
path p = complete(path(argv[1], native));
     
create_directory(p);
   }
   catch (exception& e) {
      cerr << e.what() << endl;
   }

  return(EXIT_SUCCESS);
}

The create_directory function creates a directory identified by the path argument you give it. If that directory already exists, a filesystem_error exception is thrown (derived from the standard exception class). For an explanation of the path class and complete function, both of which are part of the Boost Filesystem library, take a look at the discussion in Recipe 10.7. See Recipe 10.11 for an example of how to remove a directory and all the files it contains. If, on the other hand, portability is not a concern, consult your OS's proprietary filesystem API, which will most likely offer more flexibility.

See Also

Recipe 10.12


blog comments powered by Disqus
C++ ARTICLES

- Intel Threading Building Blocks
- Threading Building Blocks with C++
- Video Memory Programming in Text Mode
- More Tricks to Gain Speed in Programming Con...
- Easy and Efficient Programming for Contests
- Preparing For Programming Contests
- Programming Contests: Why Bother?
- Polymorphism in C++
- Overview of Virtual Functions
- Inheritance in C++
- Extending the Basic Streams in C++
- Using Stringstreams in C++
- Custom Stream Manipulation in C++
- General Stream Manipulation in C++
- Serialize Your Class into Streams in C++

Watch our Tech Videos 
Dev Articles Forums 
 RSS  Articles
 RSS  Forums
 RSS  All Feeds
Write For Us 
Weekly Newsletter
 
Developer Updates  
Free Website Content 
Contact Us 
Site Map 
Privacy Policy 
Support 

Developer Shed Affiliates

 




© 2003-2017 by Developer Shed. All rights reserved. DS Cluster - Follow our Sitemap
Popular Web Development Topics
All Web Development Tutorials