未读C中的文件++

用我刚刚检查过的代码(Ubuntu 12.04 LTS,32位)代替我之前的建议。GCC是4.7,但我很确定这是100%的标准解决方案。

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

#define desiredSize 10
#define desiredLimit 100

int main()
{
    FILE *fd = fopen("test.txt","r+");
    if (fd == NULL)
    {
        perror("open");
        exit(1);
    }

    int total = 0;
    unsigned char buff[desiredSize];

    while (total < desiredLimit)
    {
        fpos_t  position;
        fgetpos (fd, &position);

        int numberOfBytes = fread(buff, sizeof(unsigned char), desiredSize, fd);
        printf("Read try: %d\n", numberOfBytes);
        if (numberOfBytes < desiredSize)
        {
            fsetpos(fd, &position);
            printf("Return\n");
            sleep(10);
            continue;
        }
        total += numberOfBytes;
        printf("Total: %d\n", total);
    }
    return 0;
}

我从另一个控制台向文件添加文本,是的,根据我添加的内容,读取进度为5个字符块。

fseek 似乎非常适合:

FILE *fptr = fopen("test.txt","r+");
numberOfBytes = fread(buff, 1, desiredSize, fptr)
if (numberOfBytes < desiredSize) {
    fseek(fptr, -numberOfBytes, SEEK_CUR);
}

还要注意,文件描述符是 open 返回,而不是 fopen .