Re: Test failure in tac (coreutils-5.92) on Solaris

[Peter Fales]

Thanks for the quick patch!  It works for me.

For the record, this patch was also needed on HP/UX, Mac OS X, and Irix.

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On Mon, Oct 24, 2005 at 06:07:14PM +0200, Jim Meyering wrote:
> Peter Fales <address@hidden> wrote:
> > On Solaris, tac is failing when reading from stdin and stdin is a terminal.
> > (it works on Linux)  E.g. a command like this works:
> >
> >     $ echo 'a\nb' | tac
> >     b
> >     a
> >
> > But simply running tac from the command line results in getting a shell
> > prompt back (no chance to type anything):
> >
> >     $ tac
> >     $
> >
> >
> > The problem seems to be around line 548 in tac.c
> >
> >     548    file_size = lseek (fd, (off_t) 0, SEEK_END);
> >     549
> >     550    ok = (0 <= file_size
> >     551          ? tac_seekable (fd, filename)
> >     552          : tac_nonseekable (fd, filename));
> >
> > On linux lseeking on stdin returns -1, resulting in a call to
> > tac_nonseekable.  But, on Solaris, lseek returns 0.
> 
> Thanks for the detailed report.
> Here's a patch:
> 
> 2005-10-24  Jim Meyering  <address@hidden>
> 
>       * src/tac.c (tac_file): When determining whether a file is seekable,
>       also test whether it is a tty.  Using only the lseek-based test would
>       give a false positive on Solaris.  Reported by Peter Fales.
> 
> Index: src/tac.c
> ===================================================================
> RCS file: /fetish/cu/src/tac.c,v
> retrieving revision 1.125
> diff -u -p -r1.125 tac.c
> --- src/tac.c 9 Sep 2005 21:11:36 -0000       1.125
> +++ src/tac.c 24 Oct 2005 16:01:53 -0000
> @@ -547,9 +547,9 @@ tac_file (const char *filename)
>  
>    file_size = lseek (fd, (off_t) 0, SEEK_END);
>  
> -  ok = (0 <= file_size
> -     ? tac_seekable (fd, filename)
> -     : tac_nonseekable (fd, filename));
> +  ok = (file_size < 0 || isatty (fd)
> +     ? tac_nonseekable (fd, filename)
> +     : tac_seekable (fd, filename));
>  
>    if (!is_stdin && close (fd) != 0)
>      {