On Sat, Jul 26, 2025 at 09:32:27PM +0200, Dan wrote: > I have just fixed things using the let to fix $y behavior in my *pipe > technique* but nothing change: inside the pipe loop variable $arg (or > $arg1 $arg2 $arg3) seems to have a different scope than from outside > the pipe loop (passing by the environment too) ..
the lhs of a pipe will be run in a subshell so it's a complete different
process
cat /etc/passwd | while read ent;do
last_ent="$ent"
done
echo $last_ent # gone
is like
cat /etc/passwd | ( while read ent;do
last_ent="$ent"
done )
echo $last_ent # gone
fortunately, your example is a UUOC so you can instead write:
while read ent;do
last_ent="$ent"
done < /etc/passwd
echo "ent is $ent (empty by the failed read)"
echo "last ent was $last_ent"
you can use the result of any abritrary command by using a named fifo
rm -rf datastream
mkfifo datastream
getent passwd > datastream &
while read ent;do
last_ent="$ent"
done < datastream
echo "ent is $ent (empty by the failed read)"
echo "last ent was $last_ent"
rm datastream
regards
--
Marc Chantreux
Pôle CESAR (Calcul et services avancés à la recherche)
Université de Strasbourg
14 rue René Descartes,
BP 80010, 67084 STRASBOURG CEDEX
03.68.85.60.79
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