usage:	unifdef [-bBcdehKkmnsStV] [-x{012}] [-Mext] [-opath] \
		[-[i]Dsym[=val]] [-[i]Usym] [-fpath] ... [file] ...
	-Dsym=val  define preprocessor symbol with given value
	-Dsym      define preprocessor symbol with value 1
	-Usym	   preprocessor symbol is undefined
	-iDsym=val \  ignore C strings and comments
	-iDsym      ) in sections controlled by these
	-iUsym	   /  preprocessor symbols
	-fpath	file containing #define and #undef directives
	-b	blank lines instead of deleting them
	-B	compress blank lines around deleted section
	-c	complement (invert) keep vs. delete
	-d	debugging mode
	-e	ignore multiline preprocessor directives
	-h	print help
	-Ipath	extra include file path (ignored)
	-K	disable && and || short-circuiting
	-k	process constant #if expressions
	-Mext	modify in place and keep backups
	-m	modify input files in place
	-n	add #line directives to output
	-opath	output file name
	-S	list #if control symbols with nesting
	-s	list #if control symbols
	-t	ignore C strings and comments
	-V	print version
	-x{012}	exit status mode