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Date: Fri, 07 Feb 2014 16:44:10 -0500
From: "Larry Hall (Cygwin)" <reply-to-list-only-lh AT cygwin DOT com>
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To: cygwin AT cygwin DOT com
Subject: Re: get rid of getpwent? (Was: cygwin-1.7.28 getpwent header declaration changes ?)
References: <52F339CA DOT 5070305 AT gmail DOT com> <20140206090117 DOT GD2821 AT calimero DOT vinschen DOT de> <52F361C5 DOT 3000807 AT gmail DOT com> <20140206141321 DOT GI2821 AT calimero DOT vinschen DOT de> <52F40208 DOT 5030901 AT etr-usa DOT com> <20140207094917 DOT GN2821 AT calimero DOT vinschen DOT de> <52F53D7C DOT 5050201 AT etr-usa DOT com>
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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. ;-)

-- 
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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