Re^4: true from (-e "") on Windoze

My code is being fed, so to speak, by another application over which I have no control. Every now and again, when the feeder is asked for a list of files, it returns one or more elements in the array that contains just a pair of empty double quotes.

Oddly, at a Windows command prompt, you can do 'cd ""' and it does not complain. It doesn't go anywhere, but, it doesn't complain.

Comment on Re^4: true from (-e "") on Windoze

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Re^5: true from (-e "") on Windoze by afoken (Chancellor) on Jul 02, 2012 at 19:56 UTC
Oddly, at a Windows command prompt, you can do 'cd ""' and it does not complain. It doesn't go anywhere, but, it doesn't complain. Don't assume cmd.exe (or command.com) behave like a unix shell. Quite the opposite is true. 30 years of bug-compatible extensions give both a very unique smell. Whatever happens in those two dinosaurs has nearly nothing in common with the underlying APIs. Note that unquoting happens inside the application, not in the shell -- except when you call a shell buildin like cd/chdir. Now look at the fine differences: `Microsoft Windows [Version 6.1.7601] Copyright (c) 2009 Microsoft Corporation. All rights reserved. C:\Users\alex>cd C:\Users\alex C:\Users\alex>cd "" C:\Users\alex C:\Users\alex>cd . C:\Users\alex>` [download] `cd ""` behaves like `cd` without arguments, i.e. it prints the current directory. `cd .` actually changes the current directory to drumroll the current directory! So it does not print anything. Alexander -- Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)	[reply] [d/l] [select]

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Re^5: true from (-e "") on Windoze
by afoken (Chancellor) on Jul 02, 2012 at 19:56 UTC

Oddly, at a Windows command prompt, you can do 'cd ""' and it does not complain. It doesn't go anywhere, but, it doesn't complain.

Don't assume cmd.exe (or command.com) behave like a unix shell. Quite the opposite is true. 30 years of bug-compatible extensions give both a very unique smell. Whatever happens in those two dinosaurs has nearly nothing in common with the underlying APIs.

Note that unquoting happens inside the application, not in the shell -- except when you call a shell buildin like cd/chdir. Now look at the fine differences:

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Users\alex>cd
C:\Users\alex

C:\Users\alex>cd ""
C:\Users\alex

C:\Users\alex>cd .

C:\Users\alex>
[download]

cd "" behaves like cd without arguments, i.e. it prints the current directory. cd . actually changes the current directory to *drumroll* the current directory! So it does not print anything.

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

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