-r      File is readable by this user or group.
        -w      File is writable by this user or group.
        -x      File is executable by this user or group.
        -o      File is owned by this user. 
        -e      File exists.
        -z      File has zero size.
        -s      File has non-zero size (returns size).
        -f      File is a plain file.
        -d      File is a directory.
        -l      File is a symbolic link.
        -S      File is a socket.
        -b      File is a block special file.
        -c      File is a character special file.
        -u      File has setuid bit set.
        -g      File has setgid bit set.
        -k      File has sticky bit set.
        -t      Filehandle is opened to a tty.
        -T      File is a text file.
        -B      File is a binary file (opposite of -T).
        -M      Modification age (measured in days)
        -A      Acces age (measured in days)