It is a very stange problem, about Creating and Opening Files

sakiel · 08-31-2007, 12:05 AM

I made a test, i created and opened many files continuously, but not closed them. it always failed to create the new file at about the 250th file, not more than 256 files. i tried the functions, include fopen, HCreate, HopenDF, etc. All like this. I did the same work at Windows XP, it was successfully. This is very strange, do you think it is about Mac OS X system?

hayne · 08-31-2007, 01:19 AM

Every operating system has a limit on the number of files that a process is allowed to have open. The exact number varies between operating systems and is usually configurable by the system administrator.

I.e. what you experienced doesn't seem strange at all - it is quite normal. It is usually a programming error to be opening so many files without closing them.

tw · 08-31-2007, 01:42 AM

just as an added point, I suspect most systems will use a binary limit (64, 128, 256, 512, 1024...) on the number of open files, just because - hey - it's a computer. the question you're having here is probably a credit to macs. for the most part, computers have no conception of an 'appropriate' limit to the number of open files that should be allowed. old systems would simply allow you to keep opening file after file after file until something overloads and the system crashes. apparently macs have put a limit on it. I'm guessing the limit can be changed programmatically, but be glad it's there...

sakiel · 08-31-2007, 02:32 AM

yeah,u r right. i ran "unlimit -n", it shows 256.How can i change this limit.

hayne · 08-31-2007, 02:47 AM

Quote:

Originally Posted by sakiel


	yeah,u r right. i ran "unlimit -n", it shows 256.How can i change this limit.

I'm not sure - but why do you need to change it?
What are you trying to do? I.e. what is your higher-level goal?

sakiel · 08-31-2007, 04:01 AM

I created so many files as temporary files to store some image info. Not closing them is for the fast access in the future.So, it is why i need to do this.

BadgerUMD · 08-31-2007, 07:43 AM

I know it's not really an answer to your question, but ...

I'm not 100% sure why you would want to save large numbers of temporary image files but not close -- it may be faster to only keep open those files you need, as you use a lesser amount of system resources. And if you want really fast access, why write them to a file at all? Just keep them resident in memory.

08-31-2007, 12:05 AM	#1
sakiel Prospect Join Date: Jul 2007 Posts: 15	It is a very stange problem, about Creating and Opening Files I made a test, i created and opened many files continuously, but not closed them. it always failed to create the new file at about the 250th file, not more than 256 files. i tried the functions, include fopen, HCreate, HopenDF, etc. All like this. I did the same work at Windows XP, it was successfully. This is very strange, do you think it is about Mac OS X system?

08-31-2007, 01:19 AM	#2
hayne Site Admin Join Date: Jan 2002 Location: Montreal Posts: 31,956	Every operating system has a limit on the number of files that a process is allowed to have open. The exact number varies between operating systems and is usually configurable by the system administrator. I.e. what you experienced doesn't seem strange at all - it is quite normal. It is usually a programming error to be opening so many files without closing them. __________________ hayne.net/macosx.html

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08-31-2007, 01:42 AM	#3
tw Hall of Famer Join Date: Apr 2007 Posts: 4,262	just as an added point, I suspect most systems will use a binary limit (64, 128, 256, 512, 1024...) on the number of open files, just because - hey - it's a computer. the question you're having here is probably a credit to macs. for the most part, computers have no conception of an 'appropriate' limit to the number of open files that should be allowed. old systems would simply allow you to keep opening file after file after file until something overloads and the system crashes. apparently macs have put a limit on it. I'm guessing the limit can be changed programmatically, but be glad it's there...

08-31-2007, 02:32 AM	#4
sakiel Prospect Join Date: Jul 2007 Posts: 15	yeah,u r right. i ran "unlimit -n", it shows 256.How can i change this limit.

08-31-2007, 04:01 AM	#6
sakiel Prospect Join Date: Jul 2007 Posts: 15	I created so many files as temporary files to store some image info. Not closing them is for the fast access in the future.So, it is why i need to do this.

08-31-2007, 07:43 AM	#7
BadgerUMD Triple-A Player Join Date: Mar 2006 Posts: 110	I know it's not really an answer to your question, but ... I'm not 100% sure why you would want to save large numbers of temporary image files but not close -- it may be faster to only keep open those files you need, as you use a lesser amount of system resources. And if you want really fast access, why write them to a file at all? Just keep them resident in memory.