什么我读完后没有看到文件的内容？

Question

我用fwrite写入文件，然后读取文件的内容，但是当我将其打印到缓冲区并通过“printf”将其打印到标准输出时，我什么也没看到...

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

int main()
{
    uint8_t *my_buffer = malloc(64UL);

    FILE *fp1 = fopen("my_buffer_file", "w");
    fprintf(fp1, "0123456789012345678901234567890123456789012345678901234567890123");
    FILE *my_buffer_fd = fopen("my_buffer_file", "r" );
    int my_new_ret = fread(my_buffer, 1, 64UL, my_buffer_fd);
    int size = my_new_ret;
    printf("my_buffer = |%s|\n", my_buffer);
    printf("size = |%d|\n", size);


    return 0;
}

有人知道为什么会这样吗？

Answer 1

您需要先关闭 fp1，然后才能读取同一个文件，就像这样-

int main()
{
    uint8_t  *my_buffer = malloc(64UL);
    FILE *fp1 = fopen("my_buffer_file", "w");
    fprintf(fp1, "0123456789012345678901234567890123456789012345678901234567890123");

    fclose(fp1);    // New line here

    FILE *my_buffer_fd = fopen("my_buffer_file", "r" );
    int my_new_ret = fread(my_buffer, 1, 64UL ,my_buffer_fd);
    int size = my_new_ret;
    printf("my_buffer = |%s| \n", my_buffer);
    printf("size = |%d|\n", size);
    return 0;
}

输出：

my_buffer = |0123456789012345678901234567890123456789012345678901234567890123| 
size = |64|