linux 文件编程

#include<stdio.h>
#include<string.h>
#include<fcntl.h>
int main(int argc, char const *argv[])
{
    int fd, len;
    char *buf = "Hello World\n", Out[32];
    fd = open("a.txt", O_CREAT|O_TRUNC|O_RDWR,0600);
    printf("open file: a.txt fd = %d\n", fd);
    len = strlen(buf);
    int size = write(fd, buf, len);
    close(fd);
    fd = open("a.txt", O_RDWR, 0600);
    lseek(fd, 0, SEEK_SET);
    size = read(fd, Out, 12);
    printf("size = %d\nread from file:\n%s\n", size, Out);
    close(fd);
    return 0;
}