程序代码：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define BUFSIZE 1024
#define SLEN 81
void append(FILE *source,FILE *dest);

int main(void)  //把多个文件追加到一个文件中
{
    FILE *fa,*fs;
    int files=0;  //追加文件的个数
    char file_app[SLEN];  //被追加文件的名字
    char file_src[SLEN];   //源文件名字
    puts("Enter name of destination file: ");
    gets(file_app);
    if((fa=fopen(file_app,"a"))==NULL)
    {
        fprintf(stderr,"Can't open %s\n",file_app);
        exit(2);
    }
    puts("Enter name of first source file(empty line to quit): ");
    while(gets(file_src)&&file_src[0]!='\0')
    {
        if(strcmp(file_src,file_app)==0)
            fputs("Can't append file to itself\n",stderr);
        else if((fs=fopen(file_src,"r"))==NULL)
            fprintf(stderr,"Can't opem %s\n",file_src);
        else
        {
            if(setvbuf(fs,NULL,_IOFBF,BUFSIZE)!=0) //为什么要为fs创造缓存区有什么用
            {
                fputs("Can't creat input buffer\n ",stderr);
                continue;
            }
            append(fs,fa);
            if(ferror(fs)!=0)
                fprintf(stderr,"Error in reading file %s.\n",file_src);
            if(ferror(fa)!=0)
                fprintf(stderr,"Error in writing file %s.\n",file_app);
            fclose(fs);
            files++;
            printf("File %s appended.\n",file_src);
            puts("Next file(empty line to quit)");

        }
    }
    printf("Done. %d files appended.\n",files);
    fclose(fa);
    return 0;
}

void append(FILE*source,FILE *dest)
{
    size_t bytes;
    static char temp[BUFSIZE];

    while((bytes=fread(temp,sizeof(char),BUFSIZE,source))>0)  //这个循环怎么终止呀，不懂这个循环的意思
        fwrite(temp,sizeof(char),bytes,dest);
}