%{unsigned verbose;unsigned fname;char *progName;int myinput(char *buf, int max);#undef YY_INPUT#define YY_INPUT(buf,result,max) (result = myinput(buf,max))%}%s FNAME%%[ ]+         /* ignore blanks */ ;<FNAME>[ ]+  /* ignore blanks */ ;-h	|"-?"	|-help	{ printf("usage is: %s [-help | -h | -? ] [-verbose | -v]"	 " [(-file| -f) filename]\n", progName);	}-v	|-verbose { printf("verbose mode is on\n"); verbose = 1; }-f	|-file	{ BEGIN FNAME; fname = 1; }<FNAME>[^ ]+ { printf("use file %s\n", yytext); BEGIN 0; fname = 2;}[^ ]+  ECHO;%%char **targv;	/* remembers arguments */char **arglim;	/* end of arguments */main(int argc, char **argv){	progName = *argv;	targv = argv+1;	arglim = argv+argc;	yylex();	if(fname < 2)		printf("No filename given\n");}static unsigned offset = 0;/* provide a chunk of stuff to flex *//* it handles unput itself, so we pass in an argument at a time */intmyinput(char *buf, int max){	int len, copylen;	if (targv >= arglim)		return 0;	/* EOF */	len = strlen(*targv)-offset;	/* amount of current arg */	if(len >= max)		copylen = max-1;	else		copylen = len;	if(len > 0)		memcpy(buf, targv[0]+offset, copylen);	if(targv[0][offset+copylen] == '\0') {	/* end of arg */		buf[copylen] = ' ';		copylen++;		offset = 0;		targv++;	}	return copylen;}