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From: Linus Torvalds <torvalds@osdl.org>
To: Daniel Barkalow <barkalow@iabervon.org>
Cc: Paul Eggert <eggert@CS.UCLA.EDU>, Junio C Hamano <junkio@cox.net>,
	Robert Fitzsimons <robfitz@273k.net>,
	Alex Riesen <raa.lkml@gmail.com>,
	git@vger.kernel.org, Kai Ruemmler <kai.ruemmler@gmx.net>
Subject: Re: [PATCH] Try URI quoting for embedded TAB and LF in pathnames
Date: Wed, 12 Oct 2005 12:52:41 -0700 (PDT)
Message-ID: <Pine.LNX.4.64.0510121220230.15297@g5.osdl.org> (raw)
In-Reply-To: <Pine.LNX.4.63.0510121452030.23242@iabervon.org>



On Wed, 12 Oct 2005, Daniel Barkalow wrote:
> 
> I think it's actually sufficient to escape 0x00-0x1f and 0x7f; those 
> ranges are both easy

They are indeed easy.

>		 and, as far as I can tell, include all of the control 
> characters that do annoying things.

Nope. The traditional vt100 escape sequence is "ESC" followed by a 
character to indicate the type of sequence (the most common one is '['). 
That's all 7-bit and fine.

HOWEVER, they made the 8-bit extension be such that any of these vt100 
begin sequences where the second character is in the appropriate range can 
be instead shortened by one character, by instead using a single 8-bit 
character of "0x80+(char-0x40)". Ie the traditional "ESC + '['" (\x1b\x5b) 
can also be written as a single '\x9b' character, aka CSI.

In other words, 0x80-0x9f are _all_ just vt100 shorthand for ESC+'@' 
through ESC+'_'.

(I guess it's not strictly "vt100" any more - it's the extended vt220 
format).

> I think escape, backspace, delete, and 
> bell are the only ones we'd rather the terminal not get; beyond that, 
> patches with screwy filenames look screwy, but don't screw up anything 
> outside of the filename.

Try this on a (non-UTF-8) xterm:

	echo -en '\x9b5B---\x9b1A---\x9b4A\r'

and it should do:
 - move cursor 5 lines down
 - print "---"
 - move cursor 1 line up
 - print "---"
 - move cursor 4 lines up
 - return carriage to beginning.

In other words, your screen should end up looking something like this:

	[torvalds@g5 ~]$ echo -en '\x9b5B---\x9b1A---\x9b4A\r'
	[torvalds@g5 ~]$
	
	
	
	   ---
	---

where that "staircase" of two "---" things was done with cursor movements.

And that's a _benign_ sequence. You can do all kinds of funky stuff that 
really screws up the user experience. Including have the thing echo keys 
to you that you didn't type:

	echo -en '\x9b5n'

or lock the keyboard (I don't think any of the terminal emulators 
implement the latter, or some of the other stranger sequences - things to 
do double-wide characters etc).

			Linus

PS. You can do all the same in UTF-8 one, but then you'll have to add a 
\xc2 before the \x9b:

	echo -en '\xc2\x9b5B---\xc2\x9b1A---\xc2\x9b4A\r'

etc..

  reply index

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-10-07 19:35 [RFC] " Junio C Hamano
2005-10-07 23:29 ` Alex Riesen
2005-10-07 23:44   ` Junio C Hamano
2005-10-08  6:45     ` Alex Riesen
2005-10-08  9:10       ` Junio C Hamano
2005-10-08 13:30         ` [PATCH] Try URI quoting for " Robert Fitzsimons
2005-10-08 18:30           ` Junio C Hamano
2005-10-08 20:19             ` Junio C Hamano
2005-10-11  6:20               ` Paul Eggert
2005-10-11  7:37                 ` Junio C Hamano
2005-10-11 15:17                 ` Linus Torvalds
2005-10-11 18:03                   ` Paul Eggert
2005-10-11 18:37                     ` Linus Torvalds
2005-10-11 19:42                       ` Paul Eggert
2005-10-11 20:56                         ` Linus Torvalds
2005-10-12  6:51                           ` Paul Eggert
2005-10-12 14:59                             ` Linus Torvalds
2005-10-12 19:07                               ` Daniel Barkalow
2005-10-12 19:52                                 ` Linus Torvalds [this message]
2005-10-12 20:21                                   ` H. Peter Anvin
     [not found]                               ` <87vf02qy79.fsf@penguin.cs.ucla.edu>
2005-10-12 21:02                                 ` Junio C Hamano
2005-10-12 21:05                                 ` Linus Torvalds
2005-10-12 21:09                                   ` H. Peter Anvin
2005-10-12 21:15                                   ` Johannes Schindelin
2005-10-12 21:33                                   ` Junio C Hamano
2005-10-14  0:57                                   ` Paul Eggert
2005-10-14  5:43                                     ` Linus Torvalds
2005-10-12 21:24                                 ` Linus Torvalds
2005-10-14  0:16                                   ` Paul Eggert
2005-10-14  5:20                                     ` Linus Torvalds
2005-10-14 17:18                                       ` H. Peter Anvin
2005-10-14  6:59                                 ` Junio C Hamano
2005-10-09 10:42           ` Junio C Hamano

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