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

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Re^2: true from (-e "") on Windoze by CountZero (Bishop) on Jul 02, 2012 at 19:12 UTC
That won't work. Empty double quotes in a string are considered "true" by Perl. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply]
Re^3: true from (-e "") on Windoze by frozenwithjoy (Priest) on Jul 02, 2012 at 19:18 UTC
Works fine for me. Also, here is a handy table for this sort of thing: "Truth tests for different values" on True or False? A Quick Reference Guide. `defined $file`, however, would be true for an empty string. edit: Oops, I didn't catch that there were quotes inside quotes...	[reply] [d/l]
Re^4: true from (-e "") on Windoze by CountZero (Bishop) on Jul 02, 2012 at 19:42 UTC
Yep, it's the quotes-within-quotes that is the problem. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply]
Re^2: true from (-e "") on Windoze by CarolinaPerler (Acolyte) on Jul 02, 2012 at 19:15 UTC
`if ($file)` returns true, also because the variable has content, two double quotes. I think I'm going to have to just check to see if my $file variable contains a pair of double quotes and only a pair of double quotes. 'Seem like a hack, though. 'Seems like the '-e' test operator would return false on this case. That's what makes me wonder if Windoze actually uses the empty double quotes as some kind of file system object/entity. That would make the '-e' test think the empty-double-quote-thing was real and existed..... Don't know that much about the various file system types and how Perl on Windows handles them.	[reply] [d/l]
Re^3: true from (-e "") on Windoze by BillKSmith (Monsignor) on Jul 03, 2012 at 03:46 UTC
Windows uses double quotes to solve a problem caused by file (or directory) names which contain spaces. `dir "C:\Program Files\"` Works as intended `dir C:\Program Files\` File not found `dir ""` Displays current directory	[reply] [d/l] [select]
Re^3: true from (-e "") on Windoze by frozenwithjoy (Priest) on Jul 02, 2012 at 19:26 UTC
OK, how about this? (I've tested and it is working correctly for `$file = '""';` on OS X.) `for ($file) { say "nope (empty quotes)" when /""/; say "yep" when -e $file; default { say "nope (doesn't exist)"} }` [download]	[reply] [d/l] [select]
Re^4: true from (-e "") on Windoze by CarolinaPerler (Acolyte) on Jul 02, 2012 at 19:33 UTC
Yeah, the odd behavior only occurs on Windoze. UNIX/Linux/Mac work just as you'd expect, returning false for the '-e' on a pair of empty double quotes.	[reply]
Re^5: true from (-e "") on Windoze by frozenwithjoy (Priest) on Jul 02, 2012 at 21:22 UTC
Re^3: true from (-e "") on Windoze by ww (Archbishop) on Jul 02, 2012 at 22:00 UTC
I think you're misinterpreting comments preceding Re^2: true from (-e "") on Windoze; I think the fact that the VALUE of $file is -- per se -- true is borking your expectations. I don't recall any version of windows accepting `""` or `'""'` or `""""` as a filename or filename element ...or any of the DOS/doze FS using "", et al, for anything.	[reply] [d/l] [select]
Re^3: true from (-e "") on Windoze by frozenwithjoy (Priest) on Jul 02, 2012 at 19:21 UTC
Ya, I didn't catch that they were quotes within quotes. Out of curiosity, why/how is that happening?	[reply]
Re^4: true from (-e "") on Windoze by CarolinaPerler (Acolyte) on Jul 02, 2012 at 19:31 UTC
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.	[reply]
Re^5: true from (-e "") on Windoze by afoken (Chancellor) on Jul 02, 2012 at 19:56 UTC
Re^2: true from (-e "") on Windoze by CarolinaPerler (Acolyte) on Jul 02, 2012 at 19:09 UTC
Yes, it does. If I put anything between the quotes, I get the expected results. It is just the empty double quotes that unexpectedly returns true from '-e'.	[reply]