On Sun, 9 Sep 2007, Robert P. J. Day wrote:
On Sun, 9 Sep 2007, Holger Kiehl wrote:
Hello
What is the quickest way to test if a file or directory exist. I can
think of three different system calls that can be used: access(),
stat() and open(). Writting a little test program I found that this
is also the order of which is the quickest, that is access() is the
quickest and open() the slowest.
if all you want to do is check for existence, then, execution time
notwithstanding, you should use the method which accomplishes that and
nothing more, so the obvious solution would be stat().
That is what I first thought as well. But I think the problem is that
stat() needs to fill up the structure with all the data, is what takes
most the time. So I thought calling stat() as follows would solve it:
stat("abcd", NULL)
But that would fail with EFAULT (Bad address). I wonder why this is
the case, because then I assume it should be as quick as access("abcd", F_OK)
or maybe even quicker. By providing NULL as argument I tell the function
not to fillup the structure and just test if the file exist. Most proberly
POSIX defines it that way.
Holger
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