Module: FileTest

FileTest implements file test operations similar to those used in File::Stat. It exists as a standalone module, and its methods are also insinuated into the File class. (Note that this is not done by inclusion: the interpreter cheats).

Public Methods
blockdev?	Returns `true` if the named file is a block device.
chardev?	Returns `true` if the named file is a character device.
directory?	Returns `true` if the named file is a directory, `false` otherwise.
executable?	Returns `true` if the named file is executable by the effective user id of this process.
executable_real?	Returns `true` if the named file is executable by the real user id of this process.
exist?	Return `true` if the named file exists.
exists?	Return `true` if the named file exists.
file?	Returns `true` if the named file exists and is a regular file.
grpowned?	Returns `true` if the named file exists and the effective group id of the calling process is the owner of the file. Returns `false` on Windows.
identical?	Returns `true` if the named files are identical.
owned?	Returns `true` if the named file exists and the effective used id of the calling process is the owner of the file.
pipe?	Returns `true` if the named file is a pipe.
readable?	Returns `true` if the named file is readable by the effective user id of this process.
readable_real?	Returns `true` if the named file is readable by the real user id of this process.
setgid?	Returns `true` if the named file has the setgid bit set.
setuid?	Returns `true` if the named file has the setuid bit set.
size	Returns the size of `file_name`.
size?	Returns `nil` if `file_name` doesn’t exist or has zero size, the size of the file otherwise.
socket?	Returns `true` if the named file is a socket.
sticky?	Returns `true` if the named file has the sticky bit set.
symlink?	Returns `true` if the named file is a symbolic link.
writable?	Returns `true` if the named file is writable by the effective user id of this process.
writable_real?	Returns `true` if the named file is writable by the real user id of this process.
zero?	Returns `true` if the named file exists and has a zero size.

FileTest

Ruby on Rails documentation... on Rails.