Date: Wed, 28 May 1997 16:50:23 +0200 (MET DST) From: Zahemszky Gabor <zgabor@CoDe.hu> To: freebsd-questions@freebsd.org (FreeBSD questions) Cc: un_x@anchorage.net Subject: Re: What command line to redirect 'make world' warnings ? Message-ID: <199705281450.QAA00425@CoDe.hu> In-Reply-To: <Pine.BSF.3.95q.970527173802.1668B-100000@aak.anchorage.net> from Steve Howe at "May 27, 97 06:46:10 pm"
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Well, I've written RTMF, because he/she(?) wrote "in bash ..." - so maybe
(s)he HAS bash - and bash manual, too.
> > > make world 2>&1 > /proxy/world3
>
> stdout to tty
> stderr to tty
> redirection 2>&1
> stderr to stdout (tty)
> redirection > file
> stdout to file
>
> got it! i think this is an easy mistake to make, since one would assume
> if a stderr is duplicated on stdout, then any redirection of stdout would
> also apply to stderr.
After duplication - I think - they go paralell, but not on the same way. If
one of them turn, the other needn't.
> got it. i notice "make world > 2>&1 /proxy/world3" is an error,
> but "make world 2>&1 > /proxy/world3" is not! (sh)
Of course, because the ">" needs a parameter (a filename or a &foo
construct), but there isn't any.
> > &>word
> > and
> > >&word
> >
> > Of the two forms, the first is preferred.
> > This is semantically equivalent to
> >
> > >word 2>&1
> >
> > This type of redirection is working only in bash ...
>
> so with bash one could say:
>
> make world 2&>1 /proxy/world3
>
> and get the desired effect, correct? (i don't have bash ...)
No! you have to type
make world &> /proxy/world3
and it's the same as the original
command >file 2>&1
form. As I understood from the bash manual.
(Well, I didn't try your version. Maybe I'll have more time some times
later.)
> > ( make world 2>&1 >> /proxy/world3 ) > /proxy/world3
>
> in a subshell:
> stdout to tty
> stderr to tty
> redirection 2>&1
> stderr to stdout
> stdout >> file
> end subshell.
> --------------
> redirection > file
> stdout (subshell stderr) > file
>
> got it!
>
> > { make world 2>&1 >> /proxy/world3 ; } > /proxy/world3
>
> same thing with grouping instead of subshell spawning.
>
> > and you have to use append ( >> ) inside. Well, why? It's your exercise.
>
> hmmm. in sh, ">" inside works as well ... ???
Really? If it is, I think, it's a bug in shell, because first, we make the
redirection in the parent shell, after in the sub shell. But in the subshell,
with ">", we reopen it with truncation, but with ">>", with append only.
Well, I've tried it with 2.1.5's sh, with pdksh 5.2.12 and with bash 1.14.5,
and worked as I wrote. I think, in your example, you hadn't got an error
message. Try this one:
$ echo lo > file
$ ( cat nosuchfile lo 2>&1 > f ) > f ; cat f
lo
$ ( cat nosuchfile lo 2>&1 > f ) > f ; cat f
cat: nosuchfile: No such file or directory
lo
$
Well, I think maybe it's some undocumented behaviour of not a bug/not a
feature of the buffering of shell.???
Bye, Gabor
--
#!/bin/ksh
Z='21N16I25C25E30, 40M30E33E25T15U!' ;IFS=' ABCDEFGHIJKLMNOPQRSTUVWXYZ ';set $Z;for i { [[ $i = ? ]]&&print $i&&break;[[ $i = ??? ]]&&j=$i&&i=${i%?};typeset -i40 i=8#$i;print -n ${i#???};[[ "$j" = ??? ]]&&print -n "${j#??} "&&j=;typeset +i i;};IFS=' 0123456789 ';set $Z;X=;for i { [[ $i = , ]]&&i=2;[[ $i = ?? ]]||typeset -l i;X="$X $i";typeset +l i;};print "$X"
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