== == In a programming context, one usually determines whether a file is a directory using functions that access file metadata. These are dependent on the system you are programming and what language you are programming in. You should consult a reliable reference for the programming language, such as the manpages for C and C++ (in Unix-like systems) or Java's Javadocs (available on the web).

To list all files in a directory, a programmer will usually iterate across all members of the directory and print some form of information found in the file metadata, such as the filename. ---- A parent directory is the directory containing the current directory. A child directory is a directory inside of the current directory. A subdirectory is a directory inside of the current directory or any its child directories.

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In Windows, the most common way to determine if a file is a directory is using the GUI. To do this, right-click the file icon and click "Properites". If it is a directory, then the type of the file should be listed as "File Folder". Alternately, you can use the Command Prompt, which by default (Windows XP) can be accessed via the Start menu, in the Applications folder. Alternately, type "cmd" into the Run prompt (or the search field in Vista). You will be presented with a command line interface. Use the command "CD" followed by a file path to change to the desired directory, then type "DIR /A:D". This will list all files in the current directory with the attribute "directory". Alternately, you can include a path to the DIR command, such as "DIR /A:D C:\WINDOWS", to display the contents of the directory in the path.

To list all files in subfolders, use the command "DIR /S". The /S flag will cause subdirectories to be printed as well. Usage of "ls" is explained in full in the manpages, try invoking "man ls" on your system for more information. In Windows systems using the NTFS filesystem, drives are mounted as separate entities and the root folder of a drive is the drive letter, followed by a colon and a backslash (i.e. "C:").

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In Unix-like systems, the most common utility is the command "ls". Remember that such systems are case-sensitive, so capitalization matters.

To use it, open up a shell emulator, such as bash or csh, and type "cd" followed by a path to change to that directory (or include a desired path to the subsequent commands). Type "ls" to see a listing of all files in the current directory, or "ls /bin" to see a listing of all files in the directory "/bin". By adding in the arguments "l" and "a", as in the command "ls -la", you can additionally see the file permissions (starting with a 'd' if they are a directory), and the "." and ".." directories, respectively.

To display the files in all subdirectories, add the argument 'R' to your list of arguments (or just do "ls -R" if you don't require more extensive information).

Usage of "ls" is explained in full in the manpages, try invoking "man ls" on your system for more information.

If you are using the bash shell, you can use pipes ('|') to chain together several programs to do such things as search or sort your results from the previous program. For example, "ls -l | grep foo" would first list the contents of the current directory (ls), then search through them and print out only those containing the string "foo" (grep).

In most of these systems, storage devices are mounted to mountpoints, which are treated as directories within the system's directory tree. The root directory is "/". Every directory has a link to itself (".") and a link to the parent directory (".."). The root directory is special in that ".." also links back to the root directory.

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