第 13 章 文件输入/输出 （把文件附加到另一个文件末尾）

/*----------------------------------------
    append.c -- 把文件附加到另一个文件末尾
----------------------------------------*/

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

#define BUFSIZE 4096
#define SLEN 81

void append(FILE *sourse, FILE *dest);
char *s_gets(char *st, int n);

int main()
{
    FILE *fa, *fs;        //fa 指向目标文件，fs指向源文件
    int files = 0;        //附加文件的数量
    char file_app[SLEN];    //目标文件名
    char file_src[SLEN];    //源文件名
    int ch;

    puts("Enter name of destination file:");
    
    s_gets(file_app, SLEN);

    if ((fa = fopen(file_app, "a+")) == NULL)
    {
        fprintf(stderr, "Can't open %s
", file_app);
        exit(EXIT_FAILURE);
    }

    if (setvbuf(fa, NULL, _IOFBF, BUFSIZ) != 0)
    {
        fputs("Can't create output buffer
", stderr);
        exit(EXIT_FAILURE);
    }

    puts("Enter name of first source file (empty line to quit):");

    while (s_gets(file_src, SLEN) && file_src[0] != '')
    {
        if (strcmp(file_src, file_app) == 0)
            fputs("Can't append file to itself
", stderr);
        else if ((fs = fopen(file_src, "r")) == NULL)
            fprintf(stderr, "Can't open %s
", file_src);
        else
        {
            if (setvbuf(fs, NULL, _IOFBF, BUFSIZE) != 0)
            {
                fputs("Can't create input buffer
", stderr);
                continue;
            }

            append(fs, fa);

            if (ferror(fs) != 0)
                fprintf(stderr, "Error in reading file %s.
", file_src);

            if (ferror(fa) != 0)
                fprintf(stderr, "Error in writint file %s.
", file_app);

            fclose(fs);
            ++files;
            printf("File %s appended.
", file_src);
            puts("Next file (empty line to quit):");
        }
    }

    printf("Done appending. %d files appended.
", files);
    rewind(fa);
    printf("%s contents:
", file_app);
    while ((ch = getc(fa)) != EOF)
        putchar(ch);
    puts("Done displaying.");
    fclose(fa);

    return 0;
}

void append(FILE *sourse, FILE *dest)
{
    size_t bytes;
    static char temp[BUFSIZ];    //只分配一次内存

    fwrite("
", sizeof(char), strlen("
") + 1, dest);

    while ((bytes = fread(temp, sizeof(char), BUFSIZ, sourse)) > 0)
        fwrite(temp, sizeof(char), bytes, dest);
}

char *s_gets(char *st, int n)
{
    char *ret_val;
    char *find;

    if (ret_val = fgets(st, n, stdin));
    {
        if (find = strchr(st, '
'))    //查找换行符
            *find = '';
        else
            while (getchar() != '
') continue;
    }

    return ret_val;
}