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From: decot@hpisod2.HP.COM (Dave Decot)
Newsgroups: comp.sys.hp
Subject: Re: Extraneous error code under 3.1?
Message-ID: <16710035@hpisod2.HP.COM>
Date: 22 Nov 89 09:21:35 GMT
References: <JTHOMAS.89Nov17162045@tecate.nmsu.edu>
Organization: Hewlett Packard, Cupertino
Lines: 18

> >When we run the following code in either form (with the fgets or fscanf),
> >the first fgets/fscanf call returns an error code of 25 .  If that is
> >cleared, following calls do not touch errno .  Would someone else please
> >try this and report back your results?
> 
> None of this is surprising; none of the library functions in your program are
> supposed to set errno to any reasonable value.  The system calls which are
> used internally often do use and modify it, however.  In general, if the man
> page for a function doesn't say it puts an error code into "errno", assume it
> trashes it; and furthermore, even for those functions which do return codes
> in "errno", the value is only valid only if the actual function return
> indictaes that an error occurred (generally, when a system call returns -1).

All of the above is completely correct, for HP-UX 3.1.    However, please
note that all of the functions called in the program in question *do*
set errno to a reasonable value in error situations in HP-UX 7.0 or later.

Dave