Email or username:

Password:

Forgot your password?
Julia's posts Post Back to profile
Top-level
Julia Evans
8 comments
Ben Cox

@b0rk NP, sorry if that came off as "reply guy". I once spent a weekend curled up with stty.

8 July at 18:22 | Open on pgh.social
Julia Evans

@ben not at all, appreciate it -- edited the original post to link to your comment

8 July at 18:24 | Open on social.jvns.ca
Jeff Grigg

@b0rk @ben

Yes, it gets quite "hairy" with "cooked mode" and such.

The interface to ASCII terminals is based on teletypes, where the "Enter" key is "Carriage Return" (^M = 13). On output, to "go to the start of the next line," you need to send "Carriage Return" (^M) and "Line Feed" (^J).

And that's how "new lines" are stored in Windows (from MS-DOS, from CP/M), because CP/M was kind of crude and "dumb."

Unix files use '^J' for "new line." So it has to translate ("cooked mode") on I/O.

8 July at 19:53 | Open on mastodon.social
Ben Cox

@JeffGrigg @b0rk Yeah it's actually a pretty good way to get a good range of characters and consistency on input from a limited device like a tty or an early terminal.

What I had forgotten about (until someone, maybe @cks ? reminded me) is that the driver does similar transformations on output as well.

8 July at 19:58 | Open on pgh.social
Mark Eichin

@JeffGrigg
Tiny historical detail (which may be both obvious and not very relevant, I'll admit) missing here: the names are what those codes *do*, ie. Return the Carriage (or print head in fancy devices) to the first column, Feed the platen by one Line, etc. (Form Feed ^L ejecting a whole page kind of mutated to "clear"...)
@b0rk @ben

9 July at 1:26 | Open on mastodon.mit.edu
DHeadshot's Alt

@JeffGrigg
The ASCII standard specifies CRLF as a line ending: this is the rare occasion when Microsoft are following an (albeit outdated) standard when Unix-like systems aren't!
@b0rk @ben

9 July at 23:04 | Open on topspicy.social
Jeff Grigg

@ddlyh @b0rk @ben

Mainframes traditionally use fixed-width record sizes to represent "lines." (Or "cards" if you really think their way.)

Unix, C, C++ '\n'. (And '^D', not stored in the file, for end of file.)

CP/M, MS-DOS, Windows: '\r\n', the physical representation for most "terminals." (And '^Z', in the file, for "end of text in this file." With "junk" to fill the rest of the fixed-size block.)

Original Apple Mac: '\r' (or so I've read)

PICK OS: hex 'FE' character for line separator

10 July at 0:17 | Open on mastodon.social
Jeff Grigg

@ddlyh @b0rk @ben

The "logical" representation, stored in memory or disk, does not have to correspond exactly to the "physical" representation sent to the terminal/printer.

But in CP/M's case, it does simplify things: No translation; just dump text file contents to the console stream, "raw." The implementation of the "TYPE" command is "stream bytes until you hit '^Z' or end of file, and stop."

10 July at 0:20 | Open on mastodon.social
Go Up