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I'm trying to check if the path given exists. In case it doesn't, I'd like to create a folder with name given in the same directory.

Let's say pathOne: "/home/music/A" and pathTwo: "/home/music/B", such that folder A exists but folder B doesn't. Nothing happens if the path given by the user is pathOne, but if its pathTwo, then the program should realize that it doesn't exist in /home and should create it.

I know that it's possible to check the existence from files (with fopen it's possible do to that), but I don't know how to do that for folders!

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  • There is no cross-platform solution for this. What is your target OS? Commented Jun 6, 2011 at 12:34
  • @Midas Its openSUSE. P.S I expect it to be used on all Linux distros if possible. Commented Jun 6, 2011 at 12:38
  • @Midas: There are cross-platform solutions using some portability library or another and perhaps also C++0x. Still appropriate answer depends on target platforms and dependency requirements. Commented Jun 6, 2011 at 12:41

4 Answers 4

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Windows has pretty flaky support for POSIX, but this is one of those things it can do so my solution is good for Linux/Mac/POSIX/Windows):

bool directory_exists( const std::string &directory ) { if( !directory.empty() ) { if( access(directory.c_str(), 0) == 0 ) { struct stat status; stat( directory.c_str(), &status ); if( status.st_mode & S_IFDIR ) return true; } } // if any condition fails return false; } bool file_exists( const std::string &filename ) { if( !filename.empty() ) { if( access(filename.c_str(), 0) == 0 ) { struct stat status; stat( filename.c_str(), &status ); if( !(status.st_mode & S_IFDIR) ) return true; } } // if any condition fails return false; }

Note that you can easily change the argument to a const char* if you prefer that.

Also note that symlinks and such can be added in a platform specific way by checking for different values of status.st_mode.

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2 Comments

up-voted you. IMHO this is the best answer because you address the portability by hinting at the OS specific nature of the OS interfaces. BOOST is not an OS interface and it's not available in many embedded tool chains. Your mention of POSIX and Windows flaky support nice. I hate when folks just mention just use BOOST and get the golden ticket. I suppose BOOST is a valid alternative but it hides the underlying OS mechanics at play which this answer starts to involve.
Might want to #include the necessary headers for this to work.
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You should be able to use Boost Filesystem exists function. It's also portable.

There is a very good tutorial describing this very scenario, named Using status queries to determine file existence and type - (tut2.cpp)

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You can use the opendir function from 'dirent.h' and check for ENOENT as return value.

This header file is not available on Windows. On Windows you use GetFileAttributes and check for INVALID_FILE_ATTRIBUTES as return value.

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opendir is useful for listing directory, buf for just checking whether something exists it's huge overkill. Especially since on some filesystems the files in directory are in a hash or search tree, so checking whether a file exists does not involve reading content of the containing directory. Also note, that equivalent of windows GetFileAttributes in unix is stat.
@Jan Hudec: Thanks for stat. :)
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check out the boost filesystem library. It has a very convenient and high-level interface, e.g. exists(path), is_directory(path) etc.

On the Linux OS level you can use stat.

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