Switches may also be specified in a switch file using the u switch. The file may contain one or more lines of text where each line lists zero, one or more switches using the syntax above. Each line may end in a comment prefixed by the # character. The following is an example of switch file
#this is a comment line
i2 #a comment may appear at the end of a line
i5 i6 #multiple switches may appear on one line
-i7 #hyphens are optional
The switches from a switch file are processed in the order they appear in the file and the example above is equivalent to the following command line switches
i1 i2 i3 i4 i5 i6 –i7
Command line switches may be mixed with one or more switch files and are processed in the order they appear. Hence command line switches appearing after a switch file can override switches appearing within that switch file.
Switch files may also be nested to an arbitrary depth by using the “u” switch within switch files.