ref: a3b68e649d2da36d19d78106134d1114f06b56e1
dir: /testdir/T.system/
echo T.system: test system built-in
awk=${awk-../a.out}
rm -f foo
$awk 'BEGIN {
n = system("exit 3")
print n
exit n+1
}
' >foo
echo $? >>foo
echo "3
4" >foo1
diff foo foo1 || echo 'BAD: T.system (1)'