get rid of getpwent? (Was: cygwin-1.7.28 getpwent header declaration changes ?)
David Stacey
drstacey@tiscali.co.uk
Fri Feb 7 22:45:00 GMT 2014
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.
Dave.
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