tailf实现代码

最近在建立爬虫的自动化测试体系，这块要能够监测apache的access-log做验证，也就是类似tailf的功能，下面就是一个实现：

int main(int argc, char **argv) {
    char buffer[BUFSIZ];
    size_t osize, nsize;
    FILE *str;
    const char *filename;
    int count;

    if (argc != 2) {
        fprintf(stderr, "Usage: tailf logfile\n");
        exit(1);
    }

    filename = argv[1];

    //tailf(filename, 10);

    for (osize = filesize(filename);;) {
        nsize = filesize(filename);
        if (nsize != osize) {
            if (!(str = fopen(filename, "r"))) {
                fprintf(stderr, "Cannot open \"%s\" for read\n", filename);
                perror(argv[0]);
                exit(1);
            }
            if (!fseek(str, osize, SEEK_SET))
                while ((count = fread(buffer, 1, sizeof(buffer), str)) > 0)
                    fwrite(buffer, 1, count, stdout);
            fflush(stdout);
            fclose(str);
            osize = nsize;
        }
        usleep(250000); /* 250mS */
    }
    return 0;

}