CODE:

#include 
#include 
#include 

void doOneCat(const char* fileName,int* newLineFlag,
		int* nowLine,int start,int end,int printLineFlag) {
	FILE* fp=stdin;
	int buffer;
	if(fileName!=NULL) {
		fp=fopen(fileName,"r");
		if(fp==NULL) {
			fprintf(stderr,"error: failed to open file \"%s\"\n",fileName);
			exit(1);
		}
	}
	while((buffer=fgetc(fp))!=EOF) {
		if(*newLineFlag) {
			if(printLineFlag && start : set first line to output.\n");
	fprintf(stderr,"  -t : set last line to output.\n");
	exit(1);
}

int main(int argc,char* argv[]) {
	int argcCount;
	int start=0,end=0;
	int printLineFlag=0;
	int fileCameFlag=0;
	int nowLine=1;
	int newLineFlag=1;
	for(argcCount=1;argcCount<argc;argcCount++) {
		if(argv[argcCount][0]=='-') {
			if(argv[argcCount][1]==0) {
				fileCameFlag=1;
				doOneCat(NULL,&newLineFlag,&nowLine,start,end,printLineFlag);
			} else {
				if(fileCameFlag) {
					fprintf(stderr,"error: option cannot appear after file name.\n");
					exit(1);
				}
				if(strncmp(argv[argcCount],"-n",2)==0) {
					if(argv[argcCount][2]==0) {
				 		printLineFlag=1;
				 	} else {
				 		printUsage();
				 	}
				} else if(strncmp(argv[argcCount],"-h",2)==0) {
				 	char* last;
				 	start=strtod(&argv[argcCount][2],&last);
				 	if(*last!=0)printUsage();
				 	if(start<=0) {
				 		fprintf(stderr,"error: start line must be positive.\n");
				 		exit(1);
				 	}
				} else if(strncmp(argv[argcCount],"-t",2)==0) {
				 	char* last;
				 	end=strtod(&argv[argcCount][2],&last);
				 	if(*last!=0)printUsage();
				 	if(end<=0) {
				 		fprintf(stderr,"error: end line must be positive.\n");
				 		exit(1);
				 	}
				} else {
					printUsage();
				}
				if(end<start && end!=0) {
					fprintf(stderr,"error; start line cannot be larger than end line.\n");
					exit(1);
				}
			}
		} else {
			fileCameFlag=1;
			doOneCat(argv[argcCount],&newLineFlag,&nowLine,start,end,printLineFlag);
		}
	}
	if(!fileCameFlag)doOneCat(NULL,&newLineFlag,&nowLine,start,end,printLineFlag);
	return 0;
}