No, there is NO EOF character, especially in ASCII. Some systems
assign some character, or character sequence, to signal EOF. Some
historically popular choices have been:
Right.
^Z SUB Who knows why, maybe because the last letter
^D EOT End of Transmission
^Y EM End of medium
Agree; also ^C ETX End of Text. Especially in the little if ever used
ASCII-ized version of bisync, X3.20-something IIRC.
I've never seen any suggestion ESC was used by itself for EOF; it (and
to a somewhat lesser extent ^P DLE Data Link Escape) is very much used
as the prefix or introducer for a character or sequence representing
some function(s) according to many (mostly incompatible) schemes. I
could easily believe ESC-something for EOF, but not ESC alone.
^\ FS File Separator
^] GS Group Separator
^^ RS Record Separator
^_ US Unit Separator
FS or maybe GS _should_ have been used for EOF, but I've never seen it
happen. The latter two probably shouldn't.
The most commonly used sequences are: CR SUB and CR EOT as seen at
a keyboard. One system used ":EOF" at the immediate head of a line
only, i.e. preceded by CR.
Quite a few Unix (derived) programs, I believe also Multics, and
several Internet protocols perhaps inspired by them, use "period aka
dot aka full-stop alone on a line" e.g. CR . CR
In the (ITU) X.3 terminal=user interface, X.29 IIRC, you would use one
character to escape to command mode and then issue a disconnect
command. In Telenet (the now-gone company, not telnet the protocol) I
think this was return atsign D return. Similarly in most(?) telnet
clients today there is some command-escape followable by a command
conventionally 'quit'.
One system I use (sometimes) uses squiggle-letter as a way to enter
control-letter, so ~ Y means ^Y means EOF. You could count this as a
sequence or just as an encoded character.
X.25 supports grouping of packets using the 'M'ore bit, and SNA
supports grouping of RUs at two levels: chains and brackets. But these
are for arbitrary binary data not necessarily characters, and whether
such groups correspond to files or not depends on the application.
Another generic means of signalling EOF from the keyboard is the
power switch. This one may have undesirable side effects.
Or for a 'remote' terminal 'offline' or a modem/phone control.
- David.Thompson1 at worldnet.att.net