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Top Forums Programming maximum number of times - a file can be opened Post 302068709 by Perderabo on Monday 20th of March 2006 01:54:26 PM
Old 03-20-2006
I can't explain why your attempt to raise your softlimit failed.

Each open of a file creates a file table entry. The size of the file table is a kernel tunable parameter called nfile. You need to look at your own kernel to see what that is. You won't be able to use all of the file table entries repeatedly opening some file. You will need to open a few other files just to set up your attempt. Each file table entry for a file increments a counter in the vnode for that file. If you increment it to far, it would wrap around. This might not stop you from opening the file some more, but it would not be a good thing. The size of the integer that holds nfile and the size of the reference count should be the same size integer thus preventing this problem. It may be cheating, but you can have an opened file without opening a file. There are various ways to "dup" a file descriptor. The dup'ed fd points to the same file table entry as the original fd. Unix traditionally limits pid's to 32,000 (but your kernel may have a different limit). So I guess the limit is 32000 * max-fd-per-process. But again, minus a few for the overhead of reaching the point where you could try this stunt.
 

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plimit(1)							   User Commands							 plimit(1)

NAME
plimit - get or set the resource limits of running processes SYNOPSIS
plimit [-km] pid... plimit {-cdfnstv} soft,hard... pid... DESCRIPTION
If one or more of the cdfnstv options is specified, plimit sets the soft (current) limit and/or the hard (maximum) limit of the indicated resource(s) in the processes identified by the process-ID list, pid. Otherwise plimit reports the resource limits of the processes identi- fied by the process-ID list, pid. Only the owner of a process or the super-user is permitted either to get or to set the resource limits of a process. Only the super-user can increase the hard limit. OPTIONS
The following options are supported: -k On output, show file sizes in kilobytes (1024 bytes) rather than in 512-byte blocks. -m On output, show file and memory sizes in megabytes (1024*1024 bytes). The remainder of the options are used to change specified resource limits. They each accept an argument of the form: soft,hard where soft specifies the soft (current) limit and hard specifies the hard (maximum) limit. If the hard limit is not specified, the comma may be omitted. If the soft limit is an empty string, only the hard limit is set. Each limit is either the literal string unlimited, or a number, with an optional scaling factor, as follows: nk n kilobytes nm n megabytes (minutes for CPU time) nh n hours (for CPU time only) mm:ss minutes and seconds (for CPU time only) The soft limit cannot exceed the hard limit. -c soft,hard Set core file size limits (default unit is 512-byte blocks). -d soft,hard Set data segment (heap) size limits (default unit is kilobytes). -f soft,hard Set file size limits (default unit is 512-byte blocks). -n soft,hard Set file descriptor limits (no default unit). -s soft,hard Set stack segment size limits (default unit is kilobytes). -t soft,hard Set CPU time limits (default unit is seconds). -v soft,hard Set virtual memory size limits (default unit is kilobytes). OPERANDS
The following operands are supported. pid Process ID list. EXIT STATUS
plimit returns the exit value zero on success, non-zero on failure (such as no such process, permission denied, or invalid option). FILES
/proc/pid/* process information and control files ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWesu | +-----------------------------+-----------------------------+ SEE ALSO
ulimit(1), proc(1), getrlimit(2), setrlimit(2), proc(4), attributes(5), SunOS 5.10 8 Jun 1998 plimit(1)
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