Re: [ptxdist] (no subject)

[Michael Olbrich <m.olbrich@pengutronix.de>]

On Sat, Feb 21, 2015 at 11:07:55PM +0000, Rüdiger, Christoph wrote:
> I'm trying to use ptxdist on a Mac OS X system to get rid of the Linux VM
> just for compiling things. Here is the thing I stumbled upon because I
> don't get the intention and therefore struggle to find a patch.
> 
> The git commit 0dc57566bc5a25d2b086de333844a3c00addf0e4 from 2012-12-13
> changed the body of the ptxd_make_log() function in scripts/libptxdist.sh
> from this implementation
> 
> -ptxd_make_log() {
> -       #
> -       # fd3 == stdout to logfile
> -       # fd4 == stderr to logfile
> -       # fd5 == clean stdout
> -       # fd6 == clean stderr
> -       #
> -       {
> -               export PTXDIST_FD_STDOUT=5
> -               export PTXDIST_FD_STDERR=6
> -               export PTXDIST_FD_LOGFILE=7
> -               {
> -                       if [ -z "${PTXDIST_QUIET}" ]; then
> -                               ptxd_make "${@}" 4>&- |
> -                               # make's stdout on fd0
> -                               tee -a "${PTX_LOGFILE}" 2>&4 4>&- 5>&- 6>&-
> -                               check_pipe_status || return
> -                       else
> -                               exec 4>&-
> -                               ptxd_make "${@}" 1>> "${PTX_LOGFILE}"
> -                       fi
> -               } 2>&1 1>&3 3>&- 7>> "${PTX_LOGFILE}" |
> -               # make's stderr on fd0
> -               tee -a "${PTX_LOGFILE}" 1>&2 3>&- 4>&- 5>&- 6>&-
> -               check_pipe_status || return
> -       } 3>&1 4>&2 5>&1 6>&2
> -}
> 
> to this implementation
> 
> +ptxd_make_log() {(
> +       # stdout only
> +       exec {PTXDIST_FD_STDOUT}>&1
> +       # stderr only
> +       exec {PTXDIST_FD_STDERR}>&2
> +       # logfile only
> +       exec 9>> "${PTX_LOGFILE}"
> +       export PTXDIST_FD_STDOUT
> +       export PTXDIST_FD_STDERR
> +       export PTXDIST_FD_LOGFILE=9
> +
> +       if [ -z "${PTXDIST_QUIET}" ]; then
> +               # stdout and logfile
> +               exec {logout}> >(tee -a "${PTX_LOGFILE}")
> +       else
> +               # logfile only
> +               exec {logout}>> "${PTX_LOGFILE}"
> +       fi
> +       # stderr and logfile
> +       exec {logerr}> >(tee -a "${PTX_LOGFILE}" >&2)
> +
> +       ptxd_make "${@}" 1>&${logout} 2>&${logerr}
> +)}
> 
> 
> Now, my bash is complaining at the first exec command:
> 
> > exec: {PTXDIST_FD_STDOUT}: not found
> 
> 
> To me, it looks fully understandable, because {PTXDIST_FD_STDOUT} is an
> ill-formed brace expansion and is therefore ignored. But why is the Linux
> (Ubuntu 12.04) not complaining about?
> 
> What is the intention of this brace usage here?

It's valid bash syntax. A bit of history here:
The standard for sh shells says, that the file descriptors up to 9 can be
used inside the shell scripts. So that's what we used originally: With
"5>&1" we create a file descriptor that we can later use to write to stdout
when the normal stdout is redirected to the log file.
However this solution as a problem: oder scripts can use the same file
descriptor numbers and the output is send to the wrong place. This happened
e.g. with configure scripts. So we changed it to:
"exec {PTXDIST_FD_STDOUT}>&1". This is valid in bash and means that a new
file descriptor is opened (with a currently unused number >= 10) and
anything written to it is send to stdout. The file descriptor number is
stored in the specified variable (PTXDIST_FD_STDOUT).

I don't know why the bash in Max OS X cannot handle this. Maybe it's too
old? What version are you using?
Maybe something like this works:
exec 7>&1
exec 8>&1
export PTXDIST_FD_STDOUT=7
export PTXDIST_FD_STDERR=8

Regards,
Michael

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