What's the difference between using

struct passwd *getpwuid(uid_t uid);

vs

reading utmp  to get name of the person currently logged on?


Thanks in advance
Chad

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K-mart Cashier wrote:

> What's the difference between using
>
> struct passwd *getpwuid(uid_t uid);
>
> vs
>
> reading utmp  to get name of the person currently logged on?


utmp is unreliable (see utmp(5) for an explanation).

--
Kurt M. Weber
<kmw@armory.com>

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On Jul 10, 8:19 pm, "Kurt M. Weber" <k...@armory.com> wrote:
> K-mart Cashier wrote: 
> 
> 
> 
>
> utmp is unreliable (see utmp(5) for an explanation).
>
> --
> Kurt M. Weber
> <k...@armory.com>


On the Linux utmp(5), I don't see anyting that would say utmp is
unreliable.  Maybe I'm not looking at utmp(5) close enough.

Chad

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In article <1398j2g7224co6c@corp.supernews.com>,
"Kurt M. Weber" <kmw@armory.com> wrote:

> K-mart Cashier wrote:
> 
>
>
> utmp is unreliable (see utmp(5) for an explanation).

If there are multiple usernames that map to the same UID, which of the
two methods will give the one that was actually used at login time?

--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

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In article <1184129411.938641.215930@x35g2000prf.googlegroups.com>,
K-mart Cashier <cdalten@gmail.com> wrote:

> On Jul 10, 8:19 pm, "Kurt M. Weber" <k...@armory.com> wrote: 
>
> On the Linux utmp(5), I don't see anyting that would say utmp is
> unreliable.  Maybe I'm not looking at utmp(5) close enough.

I don't see it in the OS X man page, either.

--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

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K-mart Cashier wrote:

>
> On the Linux utmp(5), I don't see anyting that would say utmp is
> unreliable.  Maybe I'm not looking at utmp(5) close enough.
>
> Chad

*DESCRIPTION*
The utmp file allows one to discover information about who is
currently using the system.  There may be more users currently using the
system, because not all programs use utmp logging.

It also doesn't include logins done via xdm, since XDM login sessions aren't
assigned to a particular terminal.

Furthermore, the format for utmp varies from platform to platform.  Chances
are your code won't be portable.

--
Kurt M. Weber
<kmw@armory.com>

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