%{#undef input#undef unputunsigned verbose;unsigned fname;char *progName;%}%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;intinput(void){	char c;	if (targv >= arglim)		return(0);	/* EOF */	/* end of argument, move to the next */	if ((c = targv[0][offset++]) != '\0')		return(c);	targv++;	offset = 0;	return(' ');}/* simple unput only backs up, doesn't allow you to *//* put back different text */voidunput(int ch){	/* AT&T lex sometimes puts back the EOF ! */	if(ch == 0)		return;	/* ignore, can't put back EOF */	if (offset) {	/* back up in current arg */		offset--;		return;	}	targv--;	/* back to previous arg */	offset = strlen(*targv);}