/*
1: 编写一个程序，每次运行该程序每隔1秒就往同一个文件中写入当前的时间
        要求有行号
            1  Sat Jan 30 00:33:36 PST 2016
            2  Sat Jan 30 00:33:37 PST 2016
            3  Sat Jan 30 00:33:38 PST 2016
        按ctrl + c 停止
        再次运行该程序，继续之前的行号，往里面写下时间
            4  Sat Jan 30 00:40:38 PST 2016   
            5  Sat Jan 30 00:40:39 PST 2016   

*/

# include <stdio.h>
# include <stdlib.h>
# include <time.h>
# include <string.h>

time_t result;
char * data ;
FILE*fp;
FILE*lfp;
int count;
char buf [100];
//char lbuf [10];
int main (void)
{
   
    fp = fopen ("./a.txt","a");
    if ( fp == NULL)
    {
        perror ("fopen failed");
        return -1;
    }
   
    lfp = fopen ("./lin.txt","a+");
    if (lfp == NULL)
    {
        perror ("fopen failed");
        return -1;
    }

    lfp = freopen("./lin", "w+", lfp);
   
    //printf ("%d\n",count);
    while (1)
    {  
        //bzero (buf,100);//清空buf
        count++;
        result = time (NULL);
        data = asctime( localtime(&result));
        sprintf(buf,"%d.%s",count,data);
        fwrite (buf,strlen(buf),1,fp);//将buf里的写入fp的文件里
        fprintf(lfp, "%d\n", count);
        printf ("%s",buf);
        fseek(lfp, 0 , SEEK_SET);
        fflush (lfp);
        fflush (fp);//强退还能将buf里的存到fp的文件里
        sleep (1);
    }
   
    exit(0);
}

就是要ctrl+c强退后，再次则行要接上强退前的序号

其实不一定要处理ctri+c 可以把序号写入另一个文件“lin”中，在利用freopen重新指定到文件

是啊，忘了把文件里的内容重新读出来了，改过后的
# include <stdio.h>
# include <stdlib.h>
# include <time.h>
# include <string.h>

time_t result;
char * data ;
FILE*fp;
FILE*lfp;
int count;
char buf [100];
char lbuf [10];
int main (void)
{
   
    fp = fopen ("./a.txt","a");
    if ( fp == NULL)
    {
        perror ("fopen failed");
        return -1;
    }
   
    lfp = fopen ("./lin","a+");
    if (lfp == NULL)
    {
        perror ("fopen failed");
        return -1;
    }

    fread (lbuf,5,2,lfp);//将lfp文件的内容读到buf
    count = atoi(lbuf);//把buf中的字符转换成整数
    lfp = freopen("./lin", "w", lfp);
    while (1)
    {  
        //bzero (buf,100);//清空buf
        count++;
        result = time (NULL);
        data = asctime( localtime(&result));
        sprintf(buf,"%d.%s",count,data);
        fwrite (buf,strlen(buf),1,fp);//将buf里的写入fp的文件里
        fprintf(lfp, "%d\n", count);
        printf ("%s",buf);
        fseek(lfp, 0 , SEEK_SET);
        fflush (lfp);
        fflush (fp);//强退还能将buf里的存到fp的文件里
        sleep (1);
    }
   
    exit(0);
}