ulimit first call ok second call fail, why?
On macosx 10.7, using bash
The first call to ulimit -n succeeds, while the second fails.
a:$ ulimit -n
2560
a:$ ulimit -n 5000
a:$ ulimit -n
5000
a:$ ulimit -n 6000
bash: ulimit: open files: canno开发者_如何学Pythont modify limit: Operation not permitted
however if I try in a new shell (or another shell) to ulimit -n 6000, it succeeds:
a:$ ulimit -n
2560
a:$ ulimit -n 6000
a:$ ulimit -n
6000
Why is that?
From the bash man page:
A hard limit cannot be increased once it is set; a soft limit may be increased up to the value of the hard limit. If neither -H nor -S is specified, both the soft and hard limits are set.
Most modern *NIX's don't actually use ulimit
anymore. I'd guess that OS X has no ulimit hard max set, so your first call sets the soft and hard max, and so your second call fails every time. The first call without a [limit] parameter is probably printing the soft max.
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