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Splitting variable into two numbers

From: lisa-asket
Subject: Splitting variable into two numbers
Date: Tue, 20 Jul 2021 22:12:03 +0200 (CEST)

I could use 

-H n:m


-H n..m

From: Greg Wooledge <>
Subject: Re: Splitting variable into two numbers
Date: 20/07/2021 21:53:53 Europe/Paris

On Tue, Jul 20, 2021 at 03:37:32PM -0400, Chris F.A. Johnson wrote:
> var="{5,8}"
> IFS=, read p q <<< "${var//[\{\}]/}"
> echo "p=$p"
> echo "q=$q"

The mixing of parameter expansions (to nuke the curly braces) with
IFS-based splitting is kinda weird. I'd suggest picking one way and
using it for both steps. Either use parameter expansions exclusively
(as my earlier suggestion does), or use IFS-based splitting exclusively:

IFS='{,}' read -r _ p q _ <<< "$var"

I still prefer parameter expansions over here-string splitting for this
case, because the here-string has significantly higher overhead (it
creates a temporary file).

However, I *would* switch to here-string splitting if there were an
unknown number of elements in the input list. Then, it's justified.

(This gets us back to "where is this input coming from and why is it in
this form".)

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