Linux文件编程demo5文件光标移动操作.c

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

int main()
{
	int fd;
	char *buf = "longhaiyang hengshuai!";
    fd = open("./file1",O_RDWR);
    if(fd == -1){
		printf("文件打开失败！\n");
		fd = open("./file1",O_RDWR|O_CREAT,0600);
		if(fd >0){
			printf("创建文件成功！\n");
		}
		
		
		
	}	
	int n_write = write(fd,buf,strlen(buf));
	if(n_write != -1){
		printf("write %d byte to file1！\n",n_write);
	}
	
	char *readbuf;
	readbuf = (char *)malloc(sizeof(char)*n_write+1);
	lseek(fd,0,SEEK_SET);
	int n_read = read(fd,readbuf,n_write);
	
	printf("read %d byte to readbuf,context:%s\n",n_read,readbuf);
	close(fd);
	
}
/*
还可以通过SEEK_END计算文件的大小
int filesize = lseek(fd,0,SEEK_END);//会返回文件的大小
printf("file's size is:%d\n",filesize);



*/```