On 2/7/2014 5:45 PM, David Stacey wrote:
On 07/02/14 21:44, Larry Hall (Cygwin) wrote:
On 2/7/2014 3:09 PM, Warren Young wrote:
This takes 7.1 seconds on my system, with a 12-line /etc/passwd file:
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
int main(int argc, const char* argv[])
{
int i;
const char* user = argv[1];
if (!user) {
printf("usage: %s username\n", argv[0]);
exit(1);
}
for (i = 0; i < 1000000; ++i) {
struct passwd* pw = getpwnam(user);
if (!pw) {
printf("User %s doesn't exist!\n", user);
exit(2);
}
else if (i == 0) {
printf("User %s is UID %d\n", user, pw->pw_uid);
}
}
}
So, each getpwnam() call takes 7.1 microseconds on average.
I think you forgot to put an "exit(0);" after the last printf(). Without
it, you're checking for the same user a million times, which is certainly
going to take a little time. ;-)
I thought the point of the programme /was/ to call getpwnam() a million
times. Time this as accurately as you can. Then, with a quick division, you
get the time for one call.
Hm, I missed that he summarized with _microseconds_, even though I quoted
that too in my response. :-(
My average was much closer to 2 microseconds per call but that could be
machine differences.
In any case, sorry for the noise.
--
Larry
_____________________________________________________________________
A: Yes.
> Q: Are you sure?
>> A: Because it reverses the logical flow of conversation.
>>> Q: Why is top posting annoying in email?
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