Re: When is a file open but not open?
Re: When is a file open but not open?
- Subject: Re: When is a file open but not open?
- From: Emmanuel <email@hidden>
- Date: Sat, 6 Aug 2005 10:56:50 +0200
At 5:20 PM -0400 8/5/05, deivy petrescu wrote:
1 - you need sequential access: for instance, you want to write
several things one after the other:
write "hello"
write " "
write "world"
I disagree with you here Emmanuel.
When you write you can write wherever you want. You have to let the
script know where you want to write to.
So "write to file starting at (you fill this)" works the same way
whether opened for access or not.
You can try.
I find it not always easy to "fill this". Tell me how you would store
several records without opening the file (both for writing and for
reading) like in:
set r to open for access f with write permission
write {name:"deivy"} to r
write {name:"emmanuel"} to r
close access r
set r to open for access f
set x to read f as record
set x to read f as record
close access r
x's name
2 - you need to be sure that no-one is also writing to the file:
open with write permission does lock the file - actually I think
it's the OS' genuine mechanism to lock whatever resource might be
accessed by several clients.
Here, I really do not know and yield to Emmanuel's knowledge.
I would not do that.
There are ways around this. You could lock and unlock the file as needed.
Maybe you're right, I don't know to what extent a "locked" file is
locked. locking is something you have Finder do? Can you be sure it's
synchronous? OMM Finder's "set locked to true/false" cycle is 12
times slower (25 ms) than the "open for access/close access" cycle (2
ms.)
Emmanuel
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