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赵4老师 2014-10-31
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_chsize(fileno(f),_filelength(fileno(f))-10);
_chsize_s(fileno(f),_filelengthi64(fileno(f))-10i64);//超过2GB的文件赵4老师 2014-10-31
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赵老师说中文行吗[/quote]
英语也是一门计算机语言的说。
leftbackfielder 2014-10-31
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void ChangeFileLen(FILE *pFile)
{
assert(pFile);
fseek(pFile, 0L, SEEK_END);
int nFileLen = ftell(pFile);
if (nFileLen >= 10)
{
int nFile = _fileno(pFile);
if (_chsize(nFile, nFileLen-10) == 0)
{
printf("successfully changed!\n");
}
else
{
printf("failed changed!");
}
}
fclose(pFile);
}
mujiok2003 2014-10-30
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mujiok2003 2014-10-30
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查OS的API, FILE是流， 不可能提供这样的选项。
xspace_time 2014-10-30
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fseek(fp,10,SEEK_END);
fputc(0xFF);
fputc(0xFF);
fclose(fp);
707wk 2014-10-30
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+1
我看你有戏 2014-10-30
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赵老师说中文行吗
勤奋的小游侠 2014-10-30
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获得文件大小，然后一个字节一个字节写入新文件。写到只有10个字节时停止
poy49295 2014-10-30
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1.先用fseek,ftell获取文件大小
2.fseek回文件头，用fread逐段内容都出来，fwrite到新的文件内容，直到写入数据量是原文件数据量少10字节
mymtom 2014-10-30
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linux 下可以用ftruncate
赵4老师 2014-10-30
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_fileno
Gets the file handle associated with a stream.
int _fileno( FILE *stream );
Function Required Header Compatibility
_fileno <stdio.h> Win 95, Win NT
For additional compatibility information, see Compatibility in the Introduction.
Libraries
LIBC.LIB Single thread static library, retail version
LIBCMT.LIB Multithread static library, retail version
MSVCRT.LIB Import library for MSVCRT.DLL, retail version
Return Value
_fileno returns the file handle. There is no error return. The result is undefined if stream does not specify an open file.
Parameter
stream
Pointer to FILE structure
Remarks
The _fileno routine returns the file handle currently associated with stream. This routine is implemented both as a function and as a macro. For details on choosing either implementation, see Choosing Between Functions and Macros.
Example
/* FILENO.C: This program uses _fileno to obtain
* the file handle for some standard C streams.
*/
#include <stdio.h>
void main( void )
{
printf( "The file handle for stdin is %d\n", _fileno( stdin ) );
printf( "The file handle for stdout is %d\n", _fileno( stdout ) );
printf( "The file handle for stderr is %d\n", _fileno( stderr ) );
}
Output
The file handle for stdin is 0
The file handle for stdout is 1
The file handle for stderr is 2
Stream I/O Routines
See Also _fdopen, _filelength, fopen, freopen
赵4老师 2014-10-30
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_chsize
Changes the file size.
int _chsize( int handle, long size );
Routine Required Header Optional Headers Compatibility
_chsize <io.h> <errno.h> Win 95, Win NT
For additional compatibility information, see Compatibility in the Introduction.
Libraries
LIBC.LIB Single thread static library, retail version
LIBCMT.LIB Multithread static library, retail version
MSVCRT.LIB Import library for MSVCRT.DLL, retail version
Return Value
_chsize returns the value 0 if the file size is successfully changed. A return value of –1 indicates an error: errno is set to EACCES if the specified file is locked against access, to EBADF if the specified file is read-only or the handle is invalid, or to ENOSPC if no space is left on the device.
Parameters
handle
Handle referring to open file
size
New length of file in bytes
Remarks
The _chsize function extends or truncates the file associated with handle to the length specified by size. The file must be open in a mode that permits writing. Null characters ('\0') are appended if the file is extended. If the file is truncated, all data from the end of the shortened file to the original length of the file is lost.
Example
/* CHSIZE.C: This program uses _filelength to report the size
* of a file before and after modifying it with _chsize.
*/
#include <io.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
void main( void )
{
int fh, result;
unsigned int nbytes = BUFSIZ;
/* Open a file */
if( (fh = _open( "data", _O_RDWR | _O_CREAT, _S_IREAD
| _S_IWRITE )) != -1 )
{
printf( "File length before: %ld\n", _filelength( fh ) );
if( ( result = _chsize( fh, 329678 ) ) == 0 )
printf( "Size successfully changed\n" );
else
printf( "Problem in changing the size\n" );
printf( "File length after: %ld\n", _filelength( fh ) );
_close( fh );
}
}
Output
File length before: 0
Size successfully changed
File length after: 329678
File Handling Routines
See Also _close, _creat, _open
我看你有戏 2014-10-30
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要求，不要全部导入内存
li4c 2014-10-29
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