The wildcards * and ? may be used in filenames supplied to the plot command to plot many datafiles at once. The following, for example, would plot all datafiles in the current directory with a .dat suffix, using the same plot options:
plot '*.dat' with linewidth 2
In the graph’s legend, full filenames are displayed, allowing the datafiles to be distinguished.
If a blank filename is supplied to the plot command, the last used datafile is used again, as in the example:
plot 'data.dat' using 1:2, '' using 2:3
This can even be used with wildcards, as in the following example:
plot '*.dat' using 1:2, '' using 2:3