c - fwrite() 会让你写一些超过文件大小的东西吗？

Question

FILE *f = fopen("file.txt", "ab+");
fseek(f, NUMBER_BIGGER_THAN_FILE_SIZE, SEEK_SET);
fwrite(&someStruct, sizeof someStruct, 1l, f);

因此，如果我有类似的东西，是否可以将其写入？如果没有，我该如何实现？

Answer 1

可以覆盖文件末尾。

但是在a模式(附加模式)下，fseek对fwrite没有影响。

这在 C 标准 7.19.5.3 fopen 中有记录:

Opening a file with append mode ('a' as the first character in the mode argument) causes all subsequent writes to the file to be forced to the then current end-of-file, regardless of intervening calls to the fseek function.

来源:https://stackoverflow.com/a/5532426/2005038