* where was mention of what creates NUL files? @ 2010-09-17 18:01 Daniel Barclay 2010-09-17 18:02 ` Eric Blake ` (2 more replies) 0 siblings, 3 replies; 8+ messages in thread From: Daniel Barclay @ 2010-09-17 18:01 UTC (permalink / raw) To: cygwin Does anyone recall a mention of what in CygWin (or possibly Emacs) creates files with a simple name of "NUL"? Thanks, Daniel -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: where was mention of what creates NUL files? 2010-09-17 18:01 where was mention of what creates NUL files? Daniel Barclay @ 2010-09-17 18:02 ` Eric Blake 2010-09-17 22:46 ` Corinna Vinschen 2010-09-20 10:22 ` Oleksandr Gavenko 2013-06-27 18:35 ` g 2 siblings, 1 reply; 8+ messages in thread From: Eric Blake @ 2010-09-17 18:02 UTC (permalink / raw) To: cygwin On 09/17/2010 11:12 AM, Daniel Barclay wrote: > Does anyone recall a mention of what in CygWin (or possibly Emacs) creates > files with a simple name of "NUL"? Windows automagically maps the file named "NUL", in any directory, to the equivalent of Unix' /dev/null. Cygwin doesn't create it, but all the same, portable programs should never name a file that case-insensitively matches 'nul', 'aux', or a host of other windows-magic names: http://www.gnu.org/software/autoconf/manual/autoconf.html#File-System-Conventions Meanwhile, cygwin 1.7 has added some magic to use native NT calls to work around these limitations, so that you can have a file that appears to be named "NUL" from within cygwin, but which is really exploiting some 16-bit values outside of Unicode. But various windows programs that use windows API (rather than lower-level NT API), including your file Explorer, have a hard time figuring out what cygwin did. -- Eric Blake eblake@redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: where was mention of what creates NUL files? 2010-09-17 18:02 ` Eric Blake @ 2010-09-17 22:46 ` Corinna Vinschen 2010-09-18 3:37 ` Daniel Barclay 0 siblings, 1 reply; 8+ messages in thread From: Corinna Vinschen @ 2010-09-17 22:46 UTC (permalink / raw) To: cygwin On Sep 17 11:22, Eric Blake wrote: > On 09/17/2010 11:12 AM, Daniel Barclay wrote: > >Does anyone recall a mention of what in CygWin (or possibly Emacs) creates <finicking> It's Cygwin, not CygWin. </finicking> files with a simple name of "NUL"? > > Windows automagically maps the file named "NUL", in any directory, Meep! The Win32 API, not Windows per se. > to the equivalent of Unix' /dev/null. Cygwin doesn't create it, but > all the same, portable programs should never name a file that > case-insensitively matches 'nul', 'aux', or a host of other > windows-magic names: > > http://www.gnu.org/software/autoconf/manual/autoconf.html#File-System-Conventions > > Meanwhile, cygwin 1.7 has added some magic to use native NT calls to > work around these limitations, so that you can have a file that > appears to be named "NUL" from within cygwin, but which is really > exploiting some 16-bit values outside of Unicode. Sorry, but that's not entirely correct. There isn't any magic involved and the resulting filename is actually "nul". No mapping to the Unicode private use area. The terrible DOS device name hack, which maps filenames containing substring named like the the old DOS device names (NUL, AUX, PRN, etc) to the actual Windows device, only exists in the Win32 API. Cygwin doesn't use the Win32 API to access files, rather it uses the underlying native NT API. This API allows to create and access actual files like "nul" or "aux.c", just as on any other OS. The DOS device name hack simply doesn't affect us. So, any Cygwin application can create files like "nul". It happens, for instance, if you call something like: $ echo foo > NUL $ ls -l NUL -rw-r--r-- 1 corinna vinschen 4 Sep 17 21:25 NUL Note: Don't use DOS device names in Cygwin! Wrong: $ echo foo > NUL $ echo foo > nul $ echo foo > nul: Right: $ echo foo > /dev/null See here: http://cygwin.com/cygwin-ug-net/using-specialnames.html#pathnames-dosdevices and here: http://cygwin.com/cygwin-ug-net/using-specialnames.html#pathnames-posixdevices Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Project Co-Leader cygwin AT cygwin DOT com Red Hat -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: where was mention of what creates NUL files? 2010-09-17 22:46 ` Corinna Vinschen @ 2010-09-18 3:37 ` Daniel Barclay 0 siblings, 0 replies; 8+ messages in thread From: Daniel Barclay @ 2010-09-18 3:37 UTC (permalink / raw) To: cygwin Corinna Vinschen wrote: ... > > Note: Don't use DOS device names in Cygwin! > > Wrong: > > $ echo foo> NUL > $ echo foo> nul > $ echo foo> nul: > > Right: > > $ echo foo> /dev/null Yes, I know. I'm not using NUL (or nul or nul:, etc.), but something is. (Now I'm thinking that it's an NTEmacs problem (perhaps thinking it's running commands in a Windows/DOS shell rather than knowing it's running them in Cygwin bash.).) Daniel -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: where was mention of what creates NUL files? 2010-09-17 18:01 where was mention of what creates NUL files? Daniel Barclay 2010-09-17 18:02 ` Eric Blake @ 2010-09-20 10:22 ` Oleksandr Gavenko 2013-06-27 18:35 ` g 2 siblings, 0 replies; 8+ messages in thread From: Oleksandr Gavenko @ 2010-09-20 10:22 UTC (permalink / raw) To: cygwin On 17.09.2010 20:12, Daniel Barclay wrote: > Does anyone recall a mention of what in CygWin (or possibly Emacs) creates > files with a simple name of "NUL"? > I also use native Emacs and after some operation I got file with name NUL. I have a lot NUL files in many dirs, which can be removed only from Cygwin: $ rm NUL I don't fully debug but think this come from 'null-device' variable (which has 'NUL' value by default). To friend native GNU Emacs with Cygwin (and stop creating NUL) I use: (when (eq system-type 'windows-nt) (setq shell-file-name "bash") ;; Workaround for Cygwin shell, when set 'CYGWIN=noglob'. By default 'shell-quote-argument' ;; quoted by double '\' chars this cause failure. (defun shell-quote-argument (argument) (concat "'" argument "'") ) ;; Workaround for Cygwin when 'shell-file-name' is 'bash'. (setq null-device "/dev/null") ) -- Happy hacking! -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: where was mention of what creates NUL files? 2010-09-17 18:01 where was mention of what creates NUL files? Daniel Barclay 2010-09-17 18:02 ` Eric Blake 2010-09-20 10:22 ` Oleksandr Gavenko @ 2013-06-27 18:35 ` g 2013-06-27 19:00 ` Ken Brown 2 siblings, 1 reply; 8+ messages in thread From: g @ 2013-06-27 18:35 UTC (permalink / raw) To: cygwin Daniel Barclay <daniel <at> fgm.com> writes: > > Does anyone recall a mention of what in CygWin (or possibly Emacs) creates > files with a simple name of "NUL"? > > Thanks, > Daniel > > This has been driving me nuts for years. Finally tracked it down. These are created by emacs' man.el code when you get a man page. Reproduce: In emacs, do: M-x man <ret> <enter anything, valid ('ls') or not> Now, you'll see a NUL file in the directory. Root cause: construction of the 'man' command that is passed to the shell includes: (concat " %s 2>" null-device) The variable `null-device' is platform specific and defaults to a pure-copy of "/dev/null" which, apparently, becomes "NUL" on windows. It is a defvar in files.el and 'set' again in dos-w32.el. Resolution: In your .emacs file, do: (require 'dos-w32) ;; load this first to avoid it undo'ing the next line (setq null-device "c:/tmp/emacs-dev-null.txt") ;; set to anything Happy days! -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: where was mention of what creates NUL files? 2013-06-27 18:35 ` g @ 2013-06-27 19:00 ` Ken Brown 2013-06-27 22:32 ` wynfield 0 siblings, 1 reply; 8+ messages in thread From: Ken Brown @ 2013-06-27 19:00 UTC (permalink / raw) To: cygwin On 6/26/2013 2:53 PM, g wrote: > > > > Daniel Barclay <daniel <at> fgm.com> writes: > >> >> Does anyone recall a mention of what in CygWin (or possibly Emacs) creates >> files with a simple name of "NUL"? >> >> Thanks, >> Daniel >> >> > > > This has been driving me nuts for years. Finally tracked it down. > These are created by emacs' man.el code when you get a man page. > Reproduce: > In emacs, do: > M-x man <ret> > <enter anything, valid ('ls') or not> > Now, you'll see a NUL file in the directory. I can't reproduce this with Cygwin emacs. You must be using native Windows emacs. > Root cause: > construction of the 'man' command that is passed to the shell includes: > (concat " %s 2>" null-device) > > The variable `null-device' is platform specific and defaults to a pure-copy > of "/dev/null" which, apparently, becomes "NUL" on windows. > > It is a defvar in files.el and 'set' again in dos-w32.el. > > Resolution: > In your .emacs file, do: > > (require 'dos-w32) ;; load this first to avoid it undo'ing the next line > (setq null-device "c:/tmp/emacs-dev-null.txt") ;; set to anything Just to be clear, users of Cygwin emacs should *not* do this. Ken -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: where was mention of what creates NUL files? 2013-06-27 19:00 ` Ken Brown @ 2013-06-27 22:32 ` wynfield 0 siblings, 0 replies; 8+ messages in thread From: wynfield @ 2013-06-27 22:32 UTC (permalink / raw) To: cygwin I do not have the problem using emacs built on cygwin either. > On 6/26/2013 2:53 PM, g wrote: > > > > > > > > Daniel Barclay <daniel <at> fgm.com> writes: > > > >> > >> Does anyone recall a mention of what in CygWin (or possibly Emacs) creates > >> files with a simple name of "NUL"? > >> > >> Thanks, > >> Daniel > >> > >> > > > > > > This has been driving me nuts for years. Finally tracked it down. > > These are created by emacs' man.el code when you get a man page. > > Reproduce: > > In emacs, do: > > M-x man <ret> > > <enter anything, valid ('ls') or not> > > Now, you'll see a NUL file in the directory. > > I can't reproduce this with Cygwin emacs. You must be using native > Windows emacs. > > > Root cause: > > construction of the 'man' command that is passed to the shell includes: > > (concat " %s 2>" null-device) > > > > The variable `null-device' is platform specific and defaults to a pure-copy > > of "/dev/null" which, apparently, becomes "NUL" on windows. > > > > It is a defvar in files.el and 'set' again in dos-w32.el. > > > > Resolution: > > In your .emacs file, do: > > > > (require 'dos-w32) ;; load this first to avoid it undo'ing the next line > > (setq null-device "c:/tmp/emacs-dev-null.txt") ;; set to anything > > Just to be clear, users of Cygwin emacs should *not* do this. > > Ken > > -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2013-06-27 21:59 UTC | newest] Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2010-09-17 18:01 where was mention of what creates NUL files? Daniel Barclay 2010-09-17 18:02 ` Eric Blake 2010-09-17 22:46 ` Corinna Vinschen 2010-09-18 3:37 ` Daniel Barclay 2010-09-20 10:22 ` Oleksandr Gavenko 2013-06-27 18:35 ` g 2013-06-27 19:00 ` Ken Brown 2013-06-27 22:32 ` wynfield
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