Change the current working directory in C++

This cross-platform sample code for changing the working directory using POSIX chdir and MS _chdir as recommend in this answer. Likewise for determining the current working directory, the analogous getcwd and _getcwd are used.

These platform differences are hidden behind the macros cd and cwd.

As per the documentation, chdir's signature is int chdir(const char *path) where path is absolute or relative. chdir will return 0 on success. getcwd is slightly more complicated because it needs (in one variant) a buffer to store the fetched path in as seen in char *getcwd(char *buf, size_t size). It returns NULL on failure and a pointer to the same passed buffer on success. The code sample makes use of this returned char pointer directly.

The sample is based on @MarcD's but corrects a memory leak. Additionally, I strove for concision, no dependencies, and only basic failure/error checking as well as ensuring it works on multiple (common) platforms.

I tested it on OSX 10.11.6, Centos7, and Win10. For OSX & Centos, I used g++ changedir.cpp -o changedir to build and ran as ./changedir <path>.

On Win10, I built with cl.exe changedir.cpp /EHsc /nologo.

MVP solution

$ cat changedir.cpp

#ifdef _WIN32
#include <direct.h>
// MSDN recommends against using getcwd & chdir names
#define cwd _getcwd
#define cd _chdir
#else
#include "unistd.h"
#define cwd getcwd
#define cd chdir
#endif

#include <iostream>

char buf[4096]; // never know how much is needed

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

  if (argc > 1) {
    std::cout  << "CWD: " << cwd(buf, sizeof buf) << std::endl;

    // Change working directory and test for success
    if (0 == cd(argv[1])) {
      std::cout << "CWD changed to: " << cwd(buf, sizeof buf) << std::endl;
    }
  } else {
    std::cout << "No directory provided" << std::endl;
  }

  return 0;
}

OSX Listing:

$ g++ changedir.c -o changedir
$ ./changedir testing
CWD: /Users/Phil
CWD changed to: /Users/Phil/testing

Centos Listing:

$ g++ changedir.c -o changedir
$ ./changedir
No directory provided
$ ./changedir does_not_exist
CWD: /home/phil
$ ./changedir Music
CWD: /home/phil
CWD changed to: /home/phil/Music
$ ./changedir /
CWD: /home/phil
CWD changed to: /

Win10 Listing

cl.exe changedir.cpp /EHsc /nologo
changedir.cpp

c:\Users\Phil> changedir.exe test
CWD: c:\Users\Phil
CWD changed to: c:\Users\Phil\test

Note: OSX uses clang and Centos gnu gcc behind g++.

Now, with C++17 is possible to use std::filesystem::current_path:

#include <filesystem>
int main() {
    auto path = std::filesystem::current_path(); //getting path
    std::filesystem::current_path(path); //setting path
}

The chdir function works on both POSIX (manpage) and Windows (called _chdir there but an alias chdir exists).

Both implementations return zero on success and -1 on error. As you can see in the manpage, more distinguished errno values are possible in the POSIX variant, but that shouldn't really make a difference for most use cases.

For C++, boost::filesystem::current_path (setter and getter prototypes).

A file system library based on Boost.Filesystem will be added to the standard.