gemini://thrig.me/blog/2023/02/26/dot.gmi

. to end input is a rather old tradition in computing, which in turn is as yet young.

$ ed a pending thought is good to have between the lines we hold so dear but yet to disk these bytes are saved and float like ether from a pier hey! diddle dot dash, sang the mime whose work here is as yet unclear perhaps it was to close a rhyme or add more verse as we now fear now mimes and clowns are much the same poor sailors do they make of sea on ether waves they run git blame and from a pipe they drink to tea! with fish to catch and skel in tow and dreams of lions ever sought they ply their lines with naught to show while sings the mime--hey! diddle . a x . s/x/. . 0a a . f poem poem wq 562 $ cat poem a pending thought is good to have between the lines we hold so dear but yet to disk these bytes are saved and float like ether from a pier hey! diddle dot dash, sang the mime whose work here is as yet unclear perhaps it was to close a rhyme or add more verse as we now fear now mimes and clowns are much the same poor sailors do they make of sea on ether waves they run git blame and from a pipe they drink to tea! with fish to catch and skel in tow and dreams of lions ever sought they ply their lines with naught to show while sings the mime--hey! diddle .

The dot appears in other protocols, SMTP for example.

$ telnet localhost 25 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. 220 gear.thrig.me ESMTP OpenSMTPD HELO nurse 250 gear.thrig.me Hello nurse [127.0.0.1], pleased to meet you MAIL FROM:<jmates> 250 2.0.0 Ok RCPT TO:<jmates> 250 2.1.5 Destination address valid: Recipient ok DATA 354 Enter mail, end with "." on a line by itself Subject: test test . 250 2.0.0 3d7ff7fa Message accepted for delivery QUIT 221 2.0.0 Bye Connection closed by foreign host.

This obviously means that no line may contain . by itself. Those ahead of the curve might think to send an email that contains a . on a line by itself and then be all like "you wrong!". Hopefully they remembered to send a plaintext email, not one janked up with HTML, and for those ahead of that curve they may already know section 4.5.2 of RFC 5321.

Another method is to base64 encode the whole message, as base64 cannot generate a . on a line by itself. This however embiggens the message and may annoy certain plaintext email users, or the non-zero number of programmers who assumed that the message would not be so encoded.

The dot can also close a SSH connection, though must follow ~ and only at the beginning of a line, and assuming the EscapeChar has not been changed from the default, diddle dot!