c - 文件大小 c 不同于大小数据字符串的大小

Question

我有一个正在写入的文件，然后将其大小更改为写入其中的文本大小，例如:

FILE * file...

我从文件中获取所有数据并将文件的大小更改为数据的大小，但它有所不同。字符串的大小小于文件长度，它会剪切它并丢失数据。可能是什么问题？

while(fgets(cLine, sizeof(cLine), file) )
    str.append((string)cLine);
fputs(str.c_str(),file);
_chsize( fileno(file), (int)str.size() );

当我检查它时，fileLength(fileno(file)) 总是大于 str.size()!

Answer 1

也许是 CRLF？注意:

fopen(filename, "r") 与 fopen(filename, "rb"),

同样

fopen(filename, "w") 与 fopen(filename, "wb")。

原因是因为"r"或"w"会翻译CRLF，而"rb"或"wb" 会将数据视为二进制。在大多数平台上，这会被忽略。例如，fopen man page on OS X :

The mode string can also include the letter "b" either as a third character or as a character between the characters in any of the two-character strings described above. This is strictly for compatibility with ISO/IEC 9899:1990 ("ISO C90") and has no effect; the "b" is ignored.

fopen page on MSDN说点不一样的:

b

Open in binary (untranslated) mode; translations involving carriage-return and linefeed characters are suppressed.

If t or b is not given in mode, the default translation mode is defined by the global variable _fmode. If t or b is prefixed to the argument, the function fails and returns NULL.

For more information about using text and binary modes in Unicode and multibyte stream-I/O, see Text and Binary Mode File I/O and Unicode Stream I/O in Text and Binary Modes.