The file command can be used to print the format of the data within a file.
In this example, the data is a binary NetCDF file.
Using cat to print the file would make it look like a
monster trying to escape the terminal.
$ file trajectory_info.nc
trajectory_info.nc: data
For this one, the file is a text file that is easily printed using cat.
$ file trajectory_info.mdcrd
trajectory_info.mdcrd: ASCII text