# Fatal error: Cannot find position restraint file restraint.gro (option -r) Inquiry **URL:** \ **Category:** User discussions\ **Created:** [August 7, 2023, 1:12pm UTC](https://gromacs.bioexcel.eu/t/fatal-error-cannot-find-position-restraint-file-restraint-gro-option-r-inquiry/6978 "2023-08-07T13:12:08Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![mjsubach](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/mjsubach/32/387_2.png) [@mjsubach](https://gromacs.bioexcel.eu/u/mjsubach)\ **Post date:** [August 7, 2023, 1:12pm UTC](https://gromacs.bioexcel.eu/t/fatal-error-cannot-find-position-restraint-file-restraint-gro-option-r-inquiry/6978/1 "2023-08-07T13:12:08Z")
GROMACS version: GROMACS modification: Yes/No Here post your question: Hello upon executing the command: gmx grompp -f nvt.mdp -c em.gro -r em.gro -p topol.top -o nvt.tpr towards equalilibration of my oligomer, the above and below error precipitates: Fatal error: Cannot find position restraint file restraint.gro (option -r). From GROMACS-2018, you need to specify the position restraint coordinate files explicitly to avoid mistakes, although you can still use the same file as you specify for the -c option. is this a path problem where my present em.gro is not calling each of the posre.itp restraint files? (I do not see the posre.itp files designated in my current topol.top.) Thanks if anyone can assist me with correcting this error:) ---
**Author:** ![mjsubach](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/mjsubach/32/387_2.png) [@mjsubach](https://gromacs.bioexcel.eu/u/mjsubach)\ **Post date:** [August 9, 2023, 8:23am UTC](https://gromacs.bioexcel.eu/t/fatal-error-cannot-find-position-restraint-file-restraint-gro-option-r-inquiry/6978/2 "2023-08-09T08:23:17Z")
Hi I believe changing to zsh shell will allow the proper execution, at least it did on my end, thanks hope this helps:)