The details differ by platform.
On a Unix-alike, the GhostScript executable is usually called
gs
. The name (and possibly path) of the command is taken
first from argument gs_cmd
then from the environment variable
R_GSCMD
and default gs
. This is then looked for on the
system path and the value returned if a match is found.
On Windows, the name of the command is taken from argument
gs_cmd
then from the environment variables R_GSCMD
and
GSC
. If neither of those produces a suitable command name,
gswin64c
and gswin32c
are tried in turn. In all
cases the command is looked for on the system PATH
.
Note that on Windows (and some other OSes) there are separate
GhostScript executables to display Postscript/PDF files and to
manipulate them: this function looks for the latter.