每一次都是，無論偏移多少位元組，請問為什么不會移動到#之前寫入呢？寫入的是wanananan那一段。
uj5u.com熱心網友回復：
這個寫只能先修改記憶體里，然后重新刷寫檔案（磁盤orflash)。不能在檔案里直接插入～uj5u.com熱心網友回復：
檔案原來啥樣你想弄成啥樣
你的代碼啥樣
檔案變成啥樣
從僅有的資訊上看，一切都很正常，是你的預期或者說對檔案操作的理解不對。
uj5u.com熱心網友回復：
請看第三個引數The fseek and _fseeki64 functions moves the file pointer (if any) associated with stream to a new location that is offset bytes from origin . The next operation on the stream takes place at the new location. On a stream open for update, the next operation can be either a read or a write. The argument origin must be one of the following constants, defined in STDIO.H:
SEEK_CUR
Current position of file pointer.
SEEK_END
End of file.
SEEK_SET
Beginning of file.
You can use fseek and _fseeki64 to reposition the pointer anywhere in a file. The pointer can also be positioned beyond the end of the file. fseek and _fseeki64clears the end-of-file indicator and negates the effect of any prior ungetc calls against stream.
When a file is opened for appending data, the current file position is determined by the last I/O operation, not by where the next write would occur. If no I/O operation has yet occurred on a file opened for appending, the file position is the start of the file.
uj5u.com熱心網友回復：
原來沒有+wanan的部分，然后輸入是+wanan那部分
uj5u.com熱心網友回復：
你好，我就是只打算插入到末尾#之前的，但插到后面了，就是這個問題
uj5u.com熱心網友回復：
大佬，能否指點一下，看的不是很懂
uj5u.com熱心網友回復：
int fseek(
FILE *stream,
long offset,
int origin
);
SEEK_CUR 當前位置，偏移offset個位元組
SEEK_END 檔案末尾位置，偏移offset個位元組（offset<=0）
SEEK_SET 檔案開始位置，偏移offset個位元組（offset>=0）
uj5u.com熱心網友回復：
呼叫fseek，設定完檔案指標，再fwrite寫檔案uj5u.com熱心網友回復：
書上說寫正負都可以呀，而且可以負確實是向頭方向移動位元組。如果用fwrite可能不確定字符數比較麻煩
轉載請註明出處，本文鏈接：https://www.uj5u.com/houduan/244942.html
標籤：C語言
上一篇：C++萬能參考：常量左值參考問題