Hello, i'm working on membrane thickness in Martínez-Seara dppc article. When i use the following command: printf "%s\n" "r 1-64 & a P" "r 65-128 & a P" "q"|make_ndx -f dppc128_1.gro -o Dpp.ndx The following error appears: File Input/output error: dppc128_1.gro. Could you help me to solve it please? Alfonso