0

Can these two variable-substitution-syntaxes combined into one?

rm "$s_a/$domain.conf" 2>/dev/null
rm "$s_e/$domain.conf" 2>/dev/null

like:

rm "$s_{a,e}/$domain.conf" 2>/dev/null
  • I did a mistake not to test this. I also remember I got working results in a similar case with ${} syntax. My bad. – JohnDoea Nov 7 '18 at 1:58
5

You can, but not while quoting the expansion (since double-quotes preserve the literal meaning of most "special characters", braces included):

rm $s_{a,e}/$domain.conf

expands in steps to:

rm $s_a/$domain.conf $s_e/$domain.conf

and then to the corresponding values.

Within double-quotes, the braces are left alone, so the line expands to:

rm (value of $s_){a,e}/(value of $domain).conf

Quoting prevents unintentional expansions, notably word splitting and filename expansion. You could work around word splitting by unsetting $IFS, and could work around filename expansion with set -f, combining to:

oIFS=$IFS
IFS=
set -f
rm $s_{a,e}/$domain.conf 2>/dev/null
IFS=$oIFS
set +f
  • I can't say why other people voted as they did, just that you could help yourself by demonstrating some testing on your part and point out where you were surprised or confused. – Jeff Schaller Nov 6 '18 at 21:24
  • I fully agree this should generally be done. – JohnDoea Nov 6 '18 at 21:52
  • 2
    To not have to bother about whether set -f was in effect previously, or waht IFS was set to: ( IFS=; set -f; rm ... ) – Kusalananda Nov 6 '18 at 22:35

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