리눅스에서 fork 에러

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
 
 
int main(void){
 
	pid_t pid1;
	pid_t pid2;
	pid1= fork();
	pid2=fork();
	int status1,status2,sum1,sum2,avrg;
	FILE *rfp1;
	FILE *rfp2;
 
	char *argv[5];
	argv[0]="child";
	argv[1]="data.txt";
	argv[2]="1";
	argv[3]="50";
	argv[4]=NULL;
 
	char *argv2[5];
	argv2[0]="child";
	argv2[1]="data.txt";
	argv2[2]="51";
	argv2[3]="100";
	argv2[4]=NULL;
 
	if(pid1==0);     //첫번째 child프로세스
	{
	printf("child process- my pid : %d , parents pid : %d \n",(int)getpid(),(int)getppid());
			if(execv("./child",argv)==-1){
				perror("execv error");
				exit(1); //에러
			}
			printf("child process1");
			exit(0);
	}
 
	if(pid2==0);     //두번째 child 프로세스
	{
			printf("-->child process\n");
			if(execv("./child",argv2)==-1){
				perror("execv error");
				exit(1); //에러
			}
			printf("-->child process2");
			exit(0);
 
	}
		printf("-->parent process1");
 
		while (waitpid(pid1,&status1,WNOHANG)==0){
			printf("parent still wait pid 1");
			sleep(1);
		}
 
		while (waitpid(pid2,&status2,WNOHANG)==0){
			printf("parent still wait pid 2");
			sleep(1);
		}
		printf("child exit status : %d  %d \n",status1>>8,status2>>8);
 
 
		rfp1=fopen("result1.txt","r");
		fscanf(rfp1,"%d",&sum1);
 
		rfp2=fopen("result2.txt","r");
		fscanf(rfp2,"%d",&sum2);
		avrg= (sum1+sum2)/100;
		printf("평균은 %d이다.",avrg);
 
		return 0;
}

#include <stdio.h>
#include <stdlib.h>
 
 
//       child data.txt 1 50 NULL
int main(int argc, char** argv)
{
	FILE *rfp;
	FILE *wfp1;
	FILE *wfp2;
	int i,id,score,n,s,f,sum=0;
 
 
	 printf("child 실행 파일 실행 성공..");
 
 
 
// data.txt 받고, 파일 열기.
	if( (rfp = fopen(argv[1],"r")) == NULL)   
	{ 
		perror("fopen: data.txt");
	 exit(1); 
 
	} 
 
 
for(i=argv[2];i++;i<=argv[3]) {           
 
 
	fscanf(rfp,"%d %d",&id,&score);
	sum+=score;
		}
 
	fclose(argv[1]);
 
	if(argv[2]==1){
		wfp1=fopen("result1.txt","w");
		fputs(sum,wfp1);
		fclose("result1.txt");
	}
 
	else if(argv[2]==51){
		wfp2=fopen("result2.txt","w");
		fputs(sum,wfp2);
		fclose("result2.txt");
	}
	return 0;
}