ci-build.sh: try to fix the nbconvert loop

The error on GitHub Actions was:

  ci-build.sh: 194: read: Illegal option -d
  find: ‘standard output’: Broken pipe
  find: write error

Hopefully this updated version will work better.

Author: ctrueden

ci-build.sh

@@ -184,21 +184,20 @@ fi
 if which jupyter >/dev/null 2>&1; then
 	echo ::group::"= Jupyter notebooks ="
 	# NB: This part is fiddly. We want to loop over files even with spaces,
-	# so we use the "find ... -print0 | while read $'\0' ..." idiom.
+	# so we use the "find ... | while read ..." idiom.
 	# However, that runs the piped expression in a subshell, which means
 	# that any updates to the success variable will not persist outside
-	# the loop. So we suppress all stdout inside the loop, echoing only
-	# the final value of success upon completion, and then capture the
-	# echoed value back into the parent shell's success variable.
-	success=$(find . -name '*.ipynb' -print0 | {
-		while read -d $'\0' nbf; do
-			echo 1>&2
-			echo "== $nbf ==" 1>&2
-			jupyter nbconvert --execute --stdout "$nbf" >/dev/null
-			checkSuccess $?
-		done
-		echo $success
-	})
+	# the loop. So we store non-zero success values into a temporary file,
+	# then capture the value back into the parent shell's success variable.
+	find . -name '*.ipynb' | while read f
+	do
+		echo
+		echo "== $nbf =="
+		jupyter nbconvert --execute --stdout "$nbf"
+		checkSuccess $?
+		test "$success" -eq 0 || echo "$success" > success.tmp
+	done
+	test -f success.tmp && success=$(cat success.tmp) && rm success.tmp
 	echo ::endgroup::
 fi