GNU bug report logs - #25388
ls-quotes: kills existing scripts reading "ls" -1 as input

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Message #71 received at 25388 <at> debbugs.gnu.org (full text, mbox):

From: L A Walsh <coreutils <at> tlinx.org>
To: Eric Blake <eblake <at> redhat.com>
Cc: Paul Eggert <eggert <at> cs.ucla.edu>, Andreas Schwab <schwab <at> linux-m68k.org>,
 25388 <at> debbugs.gnu.org
Subject: Re: bug#25388: Bug in ls, kills existing scripts reading "ls" -1
 as input
Date: Mon, 09 Jan 2017 13:22:09 -0800

Eric Blake wrote:
> On 01/09/2017 02:35 PM, L A Walsh wrote:
>>     I also stand for it being strongly against GNU
>> standards to add more such behaviors.
> 
> 'ls' did not recently add any more cases where tty output differs from
> non-tty output when all other things are equal in the default state.
> All that changed was that tty output is formatted differently than it
> has been in the past. 
----
	That is not the case.

Created dir with common files w/spaces in them from people's
Doc dirs.  I also replaced the space in "My Pictures w/a tab to
see the effect -- though it wasn't necessary.


> ls
All Settings        My  Pictures    Show Desktop.scf  browser - logitech
Bluetooth Software  My Documents  Start Menu
Local Settings      Saved Games   Virtual Machines

Then I did ls the standard way:

All Settings
Bluetooth Software
Local Settings
My  Pictures
My Documents
Saved Games
Show Desktop.scf
Start Menu
Virtual Machines
browser - logitech
===
And quoted way:

'All Settings'
'Bluetooth Software'
'Local Settings'
'My'$'\t''Pictures'
'My Documents'
'Saved Games'
'Show Desktop.scf'
'Start Menu'
'Virtual Machines'
'browser - logitech'

I cut & pasted into bash, and read them into array vars using

readarray -t std
<paste>
<ctl-d>

and the same for the quoted version but 
to "readarray -t quoted".

Now I look for the files 1 at a time in a loop:
First old way (using -gG to shorten line):
-rw-rw-r-- 1 0 Jan  9 13:06 All Settings
-rw-rw-r-- 1 0 Jan  9 13:06 Bluetooth Software
-rw-rw-r-- 1 0 Jan  9 13:06 Local Settings
-rw-rw-r-- 1 0 Jan  9 13:06 My  Pictures
-rw-rw-r-- 1 0 Jan  9 13:06 My Documents
-rw-rw-r-- 1 0 Jan  9 13:06 Saved Games
-rw-rw-r-- 1 0 Jan  9 13:06 Show Desktop.scf
-rw-rw-r-- 1 0 Jan  9 13:06 Start Menu
-rw-rw-r-- 1 0 Jan  9 13:06 Virtual Machines
-rw-rw-r-- 1 0 Jan  9 13:06 browser - logitech
---
And now the new way that you claim is "the same output":

ls: cannot access 'All Settings': No such file or directory
ls: cannot access 'Bluetooth Software': No such file or directory
ls: cannot access 'Local Settings': No such file or directory
ls: cannot access 'My'$'t''Pictures': No such file or directory
ls: cannot access 'My Documents': No such file or directory
ls: cannot access 'Saved Games': No such file or directory
ls: cannot access 'Show Desktop.scf': No such file or directory
ls: cannot access 'Start Menu': No such file or directory
ls: cannot access 'Virtual Machines': No such file or directory
ls: cannot access 'browser - logitech': No such file or directory


> your claim that ls' behavior is non-standard has been proven to be
> false; I quoted the line from POSIX that explicitly permits ls
---
	By permitting it as an exception, you are admitting it
is non-standard compared to other programs.

> implementation-defined behavior when outputting to a terminal, and if it
> is permitted by the standard, then the behavior can't be considered
> non-standard.  It may not be what you want, but that does not make it
> non-standard.
---
	
> Now you are excluding a fact.  POSIX _does_ state that the output of
> 'ls' when targetting a tty is implementation-defined,
---
	I'm not quoting posix -- I'm quoting the GNU
standards you mention.


Anyway, as demonstrated above, the output is not the same and
varies based on whether or not the destination is a tty.

Your claim that the output is the same is demonstrably false.
They are not functionally equivalent.

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