Re: failure in pipeline not reflected in $?

[Chris F.A. Johnson]

On Wed, 24 Aug 2005 cell@ices.utexas.edu wrote:
> Configuration Information [Automatically generated, do not change]:
> Machine: i586
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i586' 
> -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i586-mandrake-linux-gnu' 
> -DCONF_VENDOR='mandrake' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' 
> -DSHELL -DHAVE_CONFIG_H  -I.  -I.. -I../include -I../lib  -D_GNU_SOURCE  -O2 
> -fomit-frame-pointer -pipe -march=i586 -mtune=pentiumpro
> uname output: Linux block.ices.utexas.edu 2.6.11-6mdk #1 Tue Mar 22 16:04:32 
> CET 2005 i686 AMD Athlon(TM) XP 2200+ unknown GNU/Linux
> Machine Type: i586-mandrake-linux-gnu
>
> Bash Version: 3.0
> Patch Level: 16
> Release Status: release
>
> Description:
>         I am not sure if this is a bug, or if this is correct behavior.
>
>    consider:
>
>    false | true
>    echo $?
>    0
>
>    If a command in a pipeline of commands fails, there appears to be no
>    way of knowing this.  One alternate behavior to consider is to return
>    the exit status of the first command in the pipeline to exit with non
>    zero status.

    The return codes are stored in the PIPESTATUS array:

$ false | true | false | true
$ printf "%s\n" "${PIPESTATUS[@]}"
1
0
1
0


--
    Chris F.A. Johnson                     <http://cfaj.freeshell.org>
    ==================================================================
    Shell Scripting Recipes: A Problem-Solution Approach, 2005, Apress
    <http://www.torfree.net/~chris/books/cfaj/ssr.html>