File-Directory conditionals

Conditionals regarding files and directories.

Syntax	Description
`-d PATH_TO_TEST`	True if the PATH_TO_TEST exist and it's a directory.
`-e PATH_TO_TEST`	True if the PATH_TO_TEST exist.
`-f PATH_TO_TEST`	True if the PATH_TO_TEST exist and it's a file.
`-r PATH_TO_TEST`	True if the PATH_TO_TEST exist and can be read.
`-w PATH_TO_TEST`	True if the PATH_TO_TEST exist and can be written.
`-x PATH_TO_TEST`	True if the PATH_TO_TEST exist and it's executable.
`-s PATH_TO_TEST`	True if the PATH_TO_TEST exist and it's size is greater than zero.