Bourne variable unset outside while()

Rick Miller vmiller at
Thu May 8 21:18:19 UTC 2014

Thanks, Polytropon & Matthew!

On Thu, May 8, 2014 at 4:54 PM, Polytropon <freebsd at> wrote:

> You have identified the problem: With the | redirector, a subshell
> is started which populates ${labels}, but at the "higher" level
> ${labels} keeps its setting (in this case, implicit empty string).
> Here's a workaround, using awk:
>         #!/bin/sh
>         fs="freebsd-ufs gprootfs 1G
>         freebsd-swap gpswapfs 1G
>         freebsd-ufs gpvarfs 1G"
>         labels=`echo "${fs}" | awk '{printf("%s ", $2);}'`
>         echo "labels = ${labels}"
> In this example, with `...`, which is the same as $(...), also
> starts a subshell, but assigns its output to a variable, so there
> will be no scope problem. This idea uses the advantage that your
> delimiter is newline, and awk can process the input line per line,
> printing "incomplete lines" (no newline added) as output.
> The result will be:
>         labels = gprootfs gpswapfs gpvarfs
> Is this what you expected?

Wow!  It's soooo obvious to me now that you've pointed it out.  I don't
often use while read's in this manner.  Thanks for the feedback!

Take care
Rick Miller

More information about the freebsd-questions mailing list