GNU bug report logs - #4115
grep and null device

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Message #5 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: ts011c8050 <at> blueyonder.co.uk
To: bug-gnu-emacs <at> gnu.org
Subject: grep and null device
Date: Tue, 11 Aug 2009 09:41:50 +0100 (BST)

Using emacs 23.1.1 on Windows ( also saw it on emacs 22.x and upgraded )
grep is from cygwin "GNU grep 2.5.3"


Using rgrep always tags on a null device giving lots of output like

grep: NUL: No such file or directory
grep: NUL: No such file or directory
grep: NUL: No such file or directory
grep: NUL: No such file or directory
grep: NUL: No such file or directory

I've tried customising and turning of grep-use-null-device - as from a
quick look at grep.el this is responsible. But no success.

Bug recreated using -no-init-file and -no-site-file



In GNU Emacs 23.1.1 (i386-mingw-nt5.1.2600)
 of 2009-07-30 on SOFT-MJASON
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.4)'

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: ENG
  value of $XMODIFIERS: nil
  locale-coding-system: cp1252
  default-enable-multibyte-characters: t

Major mode: Custom

Minor modes in effect:
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
M-x r e g <backspace> <backspace> g r e p <return>
<return> * . a s <return> C-a C-k $ F L A S H / <tab>
<return> <backspace> <return> <left> <left> <left>
<left> <left> <left> <left> <left> <left> <left> <left>
<left> <left> <left> <left> <left> <left> <left> <right>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<right> L : <backspace> <backspace> : <return> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<menu-bar> <options> <customize> <customize-group>
g r e p <return> <help-echo> <down-mouse-1> <mouse-1>
<wheel-down> <double-wheel-down> <triple-wheel-down>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <down-mouse-1> <help-echo> <mouse-movement>
<drag-mouse-1> <help-echo> <down-mouse-1> <help-echo>
<down-mouse-1> <help-echo> <help-echo> <down-mouse-1>
<mouse-1> M-x r g r e p <return> <return> <return>
<return> <help-echo> <down-mouse-1> <mouse-1> <wheel-down>
<double-wheel-down> M-x r g r e p <return> <return>
<return> <return> <help-echo> <down-mouse-1> <mouse-1>
M-x r e p o r t - e m <tab> <return>

Recent messages:
Creating group...
Creating group members... 91%
Creating group magic...
Creating group state...
Creating group... done
Creating customization items ...done
Resetting customization items...done
Creating customization setup...done
To install your edits, invoke [State] and choose the Set operation
Grep finished (matches found) [2 times]

Message #10 received at 4115 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: ts011c8050 <at> blueyonder.co.uk, 4115 <at> debbugs.gnu.org
Subject: Re: bug#4115: grep and null device
Date: Tue, 11 Aug 2009 21:40:42 +0300

> Date: Tue, 11 Aug 2009 09:41:50 +0100 (BST)
> From: ts011c8050 <at> blueyonder.co.uk
> Cc: 
> 
> Using emacs 23.1.1 on Windows ( also saw it on emacs 22.x and upgraded )
> grep is from cygwin "GNU grep 2.5.3"
> 
> 
> Using rgrep always tags on a null device giving lots of output like
> 
> grep: NUL: No such file or directory

Does Cygwin support NUL as the Windows null device?  If not, that's
your problem.

Doesn't `rgrep' also invoke `find'?  (It should show the full command
it is running in the "*grep*" buffer.)  If so, what port of `find' are
you using?

Message #15 received at 4115 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: shippeys <theshippeys <at> blueyonder.co.uk>
Cc: 4115 <at> debbugs.gnu.org
Subject: Re: bug#4115: grep and null device
Date: Tue, 11 Aug 2009 23:34:57 +0300

> From: "shippeys" <theshippeys <at> blueyonder.co.uk>
> Date: Tue, 11 Aug 2009 19:53:05 +0100

Please use Reply-All, to let the bug-tracker archive all the
discussion.

> > > grep: NUL: No such file or directory
> > 
> > Does Cygwin support NUL as the Windows null device?  If not, that's
> > your problem.
> > 
> 
> Yes - Would it be the grep.el code that gets confused and picks NUL?

You are using a native Windows port of Emacs.  NUL is the standard
name of the null device on that system.  Why do you think it gets
confused?

> AIUI the null device is only there to make sure the grep call doesn't hang
> if you forget to pass it files to search. It seems a lot of pain for a
> marginal benefit!

I don't know yet why null device is there.  Seeing the command line
would help.

Message #20 received at 4115 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Jason Rumney <jasonr <at> gnu.org>
To: Eli Zaretskii <eliz <at> gnu.org>, 4115 <at> debbugs.gnu.org
Cc: shippeys <theshippeys <at> blueyonder.co.uk>
Subject: Re: bug#4115: grep and null device
Date: Wed, 12 Aug 2009 06:47:41 +0800

Eli Zaretskii wrote:

>> AIUI the null device is only there to make sure the grep call doesn't hang
>> if you forget to pass it files to search. It seems a lot of pain for a
>> marginal benefit!
>>     
>
> I don't know yet why null device is there.  Seeing the command line
> would help.
>   

It is there to force grep to print filenames in its output, even if only 
a single filename is given on the command line.

Message #25 received at 4115 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Tom Shippey <tomshippey <at> blueyonder.co.uk>
Cc: 4115 <at> debbugs.gnu.org
Subject: Re: bug#4115: grep and null device
Date: Wed, 12 Aug 2009 06:10:24 +0300

> From: "Tom Shippey" <tomshippey <at> blueyonder.co.uk>
> Date: Tue, 11 Aug 2009 23:00:38 +0100
> 
> find . \( -path \*/SCCS -o -path \*/RCS -o -path \*/CVS -o -path \*/MCVS -o
> -path \*/.svn -o -path \*/.git -o -path \*/.hg -o -path \*/.bzr -o -path
> \*/_MTN -o -path \*/_darcs -o -path \*/\{arch\} \) -prune -o  -type f \(
> -iname \*.c \) -exec grep -i -n junk {} NUL \;
> ./x.c:1:junk
> ./x.c:3:junk
> grep: NUL: No such file or directory
> grep: NUL: No such file or directory

Does it help to set null-device to "/dev/null"?

Message #30 received at 4115-done <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Tom Shippey <tomshippey <at> blueyonder.co.uk>
Cc: 4115-done <at> debbugs.gnu.org
Subject: Re: bug#4115: grep and null device
Date: Wed, 12 Aug 2009 20:32:38 +0300

> From: "Tom Shippey" <tomshippey <at> blueyonder.co.uk>
> Date: Wed, 12 Aug 2009 08:50:57 +0100
> 
> > > find . \( -path \*/SCCS -o -path \*/RCS -o -path \*/CVS -o -path
> > \*/MCVS -o
> > > -path \*/.svn -o -path \*/.git -o -path \*/.hg -o -path \*/.bzr -o -
> > path
> > > \*/_MTN -o -path \*/_darcs -o -path \*/\{arch\} \) -prune -o  -type f
> > \(
> > > -iname \*.c \) -exec grep -i -n junk {} NUL \;
> > > ./x.c:1:junk
> > > ./x.c:3:junk
> > > grep: NUL: No such file or directory
> > > grep: NUL: No such file or directory
> > 
> > Does it help to set null-device to "/dev/null"?
> 
> Yep - that works fine. Many thanks.

Thanks.  I'm closing the bug, because its reason is mixing a native
Windows build of Emacs with Cygwin shell that apparently does not
support NUL as the null device.

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