On Tue, 20 Dec 2022 at 21:10, The Wanderer <wande...@fastmail.fm> wrote:
> On 2022-12-20 at 02:51, Thomas Schmitt wrote:
> >>> offst=$( expr \
> >>> $( grep -a -o -b -m 1 CD001 cdimage.iso \
> >>> | sed -e 's/:/ /' \
> >>> | awk '{ print $1 }' ) - 32769 )
> >
> > The Wanderer wrote:
> >> Cutting down the command line led me to discover that even with '-m 1',
> >> four different numbers are printed by the grep-pipeline subshell.
> >> (Without '-m 1', seven are printed.)
> >
> > This contradicts the promises of man grep about option -m.
>
> It does seem to, at least at a glance - but I think I've figured out
> what's going on, and it's actually consistent with the option set you
> gave.
[...]
Hi,
Slightly offtopic rambling ...
I haven't looked at the 'grep' part of the above expression, but
I assume that its output lines look something like:
100:CD001
If that is the case, then awk does not need any assistance
from 'expr' or 'sed' (and even not from 'grep' if we were not
searching a binary file).
Short demo:
$ echo 100:CD001 | awk 'BEGIN { FS=":" } /CD001/ { print $1 - 50 }'
50
I only write this because I just magine how poor old 'awk' feels:
"don't embed me in this pipelines and subshells and unnecessary
commands, I can do all that stuff myself without any help!!".
