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From: Peter da Silva <peter@bonkers.taronga.com>
Message-Id: <199504162359.SAA02555@bonkers.taronga.com>
Subject: Re: aspfilter & stdin
To: rpt@miles.sso.loral.com (Richard Toren)
Date: Sun, 16 Apr 1995 18:59:52 -0500 (CDT)
Cc: hackers@FreeBSD.org
In-Reply-To: <Pine.SUN.3.91.950416174558.11362A-100000@miles> from "Richard Toren" at Apr 16, 95 05:54:29 pm
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> I have modified the 'rewindstdin.c' as:

>    #include <stdio.h>
>    #include <unistd.h>

>    main()
>    {
>      return lseek(0,0L,SEEK_SET) < 0; 
>    }

> Giving the following results:
>    <src/rewind-stdin># make
>    cc -s -O -o rewindstdin rewindstdin.c
>    <src/rewind-stdin># cat rewindstdin.c | (file -; ./rewindstdin ;file -) 
>    standard input:              c program text
>    standard input:              empty

You can't rewind a pipe.

Period.

Try "(file - ; ./rewindstdin ; file -)  < rewindstdin.c".

> ?? why the '< 0' of the return code??

RETURN VALUES
     Upon successful completion, lseek() returns the resulting offset location
     as measured in bytes from the beginning of the file.  Otherwise, a value
     of -1 is returned and errno is set to indicate the error.

It should be "return lseek(0,0L,SEEK_SET) == -1;"

I don't believe that any other nonzero result is possible in this case, but
it's always better to check for the documented return value.