多进程拷贝大文件

主要运用了进程创建 mmap映射区等知识点

#include<stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#include <sys/wait.h>

int main(){

	int new_fd,old_fd,i;
	long int size;
	char *p_old, *p_new;
	pid_t pid;
	old_fd = open("src.txt", O_RDWR,0644);//源文件 自己设定
	if (old_fd < 0){
		perror("open error\n");
		exit(1);
	}
	size = lseek(old_fd, 0, SEEK_END);
	p_old = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, old_fd, 0);
//////////////////////////////////////////
	new_fd = open("result", O_RDWR | O_CREAT | O_TRUNC, 0644);
	if (new_fd < 0){
		perror("open error\n");
		exit(1);
	}
	ftruncate(new_fd, size);
	p_new = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, new_fd, 0);
/////////////////////////////////////////////
	size = lseek(old_fd, 0, SEEK_END);
	long int cut = size / 5;//进程为5
	long int yu = size % 5;//
	for(i=0; i<5; i++){
		pid = fork();
		if(pid == 0)
			break;
	}
	if(i<=3){
		printf("pid = %d\n", getpid());
		memcpy(p_new+i*cut,p_old+i*cut,cut);
	}else if(i==4){
		printf("pid = %d\n", getpid());
		memcpy(p_new+i*cut,p_old+i*cut,cut+yu);
	}else{
		int j;
		pid_t pid2;
		for(j=0; j<5;j++){
			while((pid2=waitpid(-1, NULL,WNOHANG)) == 0 && pid2 != -1);
			printf("---pid2=%d\n", pid2);
		}
	}
	return 0;
}

来源：CSDN

作者：a__white

链接：https://blog.csdn.net/a__white/article/details/104526393

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