line_number.c

#include <stdio.h>
int main(){
 
	
	FILE *ff;
	char s[255];
	ff=fopen(__FILE__,"r");
	int num=0;
	while(fgets(s,255,ff)){		
		num++;
		printf("%d %s",num,s);
	}
 
	
	fclose(ff);
	return 0;
	
}
========with filename==========
#include <stdio.h>
#include <stdlib.h>
int main(int c, char *argv[]){
 
	if(c!=2){
	  puts("please input filename");	
	  exit(0);	
	}
	FILE *ff;
	char s[255];
	ff=fopen(argv[1],"r");
	int num=0;
	while(fgets(s,255,ff)){		
		num++;
		printf("%d %s",num,s);
	}
 
	
	fclose(ff);
	return 0;
	
}