linux c 向文件中插入一段数据~~

编写C程序完成：创建一个新文件，输入一段数据，然后随机移动指针接着插入一段数据。完成后，查看该文件的大小和内容。

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

#define MAXSIZE 1024

int main(int argc,char **argv)
{
    int fp;
    int ran_num,r_num,w_num,t_num;
    char buf[MAXSIZE],head[MAXSIZE],tail[MAXSIZE];
    struct stat f_stat;

    if(argc!=2)
    {
        printf("Usage: ./fc filename \n");
        exit(-1);
    }

    if(access(argv[1],F_OK)==0)
    { /* 检测文件是否已存在 */
        printf("File %s existed !\n",argv[1]);
        exit(-1);
    }

    if((fp=open(argv[1],O_WRONLY|O_CREAT,00644))==-1)
    { /* 创建文件 */
        perror("Creat file");
        exit(-1);
    }
    
    printf("Input some data:\n");
    if((r_num=read(1,buf,MAXSIZE))<0)
    { /* 读数据到BUF中 */
        perror("First Read");
         exit(-1);
    }
    
    if((w_num=write(fp,buf,r_num))==-1)
    { /* 写如数据到文件中 */
        perror("First Write");
        exit(-1);
    }

    if(fstat(fp,&f_stat)==-1)
    { /* 获取文件信息 */
        perror("Fstat error");
        exit(-1);
    }

    printf("The file size is %d bytes\n",f_stat.st_size);
    close(fp);
        
    if((fp=open(argv[1],O_RDWR))==-1)
    { /* 创建文件 */
        perror("Open file");
        exit(-1);
    }
   /* 实现随机数 */    
    ran_num=random();
    
    lseek(fp,ran_num%f_stat.st_size,SEEK_SET);

    if((t_num=read(fp,tail,MAXSIZE))==-1)
    {
        perror("Tail error");
        exit(-1);
    }

    lseek(fp,ran_num%f_stat.st_size,SEEK_SET);
    
    bzero(buf,MAXSIZE);
    if((r_num=read(1,buf,MAXSIZE))<0)
    { /* 读数据到BUF中 */
        perror("Second Read");
         exit(-1);
    }

    if((w_num=write(fp,buf,r_num-1))==-1)
    { /* 写如数据到文件中 */
        perror("Second Write");
        exit(-1);
    }

    if(write(fp,tail,t_num)==-1)
    { /* 写如数据到文件中 */
        perror("TailWrite");
        exit(-1);
    }

    lseek(fp,0,SEEK_SET);

    if(read(fp,buf,MAXSIZE)==-1)
    {
        perror("Last Read");
        exit(-1);
    }

    close(fp);
    if(stat(argv[1],&f_stat)==-1)
    { /* 获取文件信息 */
        perror("Fstat error");
        exit(-1);
    }

    printf("The content of file is :\n%s",buf);
    
    printf("The file size is %d bytes\n",f_stat.st_size);

    return 0;

}

结果:

zuii@zuii-desktop:~/c/sy$ ./fc hello
Input some data:
1111111111111111
The file size is 17 bytes
222222222222222222
The content of file is :
1111111111222222222222222222111111
The file size is 35 bytes