Hi Alf,
welcome here

If it says no such file or directory, then ther is a nameing problem.
I beleive, you are running this on a UNIX/LINUX host?
You are propably only used to Windows?
Here are some very important differences:
UNIX does nor only display capital letters in a filename, it recognizes the difference.
GuestBook.txt is not the same as guestbook.txt or GuestBook.TXT .
Never use the backslash (\) for paths, UNIX uses the normal slash (/).
After you are running a webserver (usualy APACHE), /filename is not a file in the systems root, it is the file in the webspace root.
Look for all these aspects and locate the file with your ftp client and then adapt the filename and path to what you find there.