This is a quick-and-dirty method of guessing a file's classes (hence the g in gclass()).

gclass(x, n = 6L, ...)

Arguments

x
A file to read lines from and guess its columns' classes.
n
The number of lines you want gclass() to read. Default is 6.
...
Other parameters to pass to gclass(). See Details.

Details

gclass() makes an estiamte as to which read function to use. For example, if you pass the parameter widths then gclass assumes you are trying to read from a fixed-width file and so uses read.fwf to read the number of lines specified by the parameter n.