Couldn't run gmx trjconv

GROMACS version: 2020.4
i tried to run

gmx trjconv -f file.xtc -o file.pdb

but got

Program: gmx trjconv, version 2020.4
Source file: src/gromacs/utility/futil.cpp (line 480)

File input/output error:

the file.xtc exists but couldn’t resolve this problem

You need to supply a .tpr file if you want to write output in PDB format from a trajectory (which does not have any concept of atom or residue names, numbers, etc). You did not specify one, so trjconv is looking for the default file name. It didn’t find it, hence the error.

Thanks for helping … it’s done