File Handling

Use these routines to create, delete, and manipulate files and to set and check file-access permissions.

The C run-time libraries have a 512 limit for the number of files that can be open at any one time. Attempting to open more than the maximum number of file descriptors or file streams causes program failure. Use _setmaxstdio to change this number.

The following routines operate on files designated by a file descriptor.

File-Handling Routines (File Descriptor)

Routine	Use	.NET Framework equivalent
_chsize,_chsize_s	Change file size	System::IO::Stream::SetLength, System::IO::FileStream::SetLength
_filelength, _filelengthi64	Get file length	System::IO::Stream::Length, System::IO::FileStream::Length
_fstat, _fstat32, _fstat64, _fstati64, _fstat32i64, _fstat64i32	Get file-status information on descriptor	Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_get_osfhandle	Return operating-system file handle associated with existing C run-time file descriptor	Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_isatty	Check for character device	System::IO::Stream::CanWrite, System::IO::FileStream::CanWrite
_locking	Lock areas of file	System::IO::FileStream::Lock
_open_osfhandle	Associate C run-time file descriptor with existing operating-system file handle	System::IO::FileStream::Handle
_setmode	Set file-translation mode	System::IO::BinaryReader Class, System::IO::TextReader Class

The following routines operate on files specified by a path or filename.

File-Handling Routines (Path or Filename)

Routine	Use	.NET Framework equivalent
_access, _waccess, _access_s, _waccess_s	Check file-permission setting	System::IO::FileAccess Enumeration
_chmod, _wchmod	Change file-permission setting	System::IO::File::SetAttributes, System::Security::Permissions::FileIOPermission
_fullpath, _wfullpath	Expand a relative path to its absolute path name	System::IO::File::Create
_makepath, _wmakepath, _makepath_s, _wmakepath_s	Merge path components into single, full path	System::IO::File::Create
_mktemp, _wmktemp, _mktemp_s, _wmktemp_s	Create unique filename	Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
remove, _wremove	Delete file	System::IO::File::Delete
rename, _wrename	Rename file	System::IO::File::Move
_splitpath, _wsplitpath, _splitpath_s, _wsplitpath_s	Parse path into components	Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_stat, _stat64, _stati64, _wstat, _wstat64, _wstati64	Get file-status information on named file	System::IO::File::GetAttributes, System::IO::File::GetCreationTime, System::IO::File::GetLastAccessTime, System::IO::File::GetLastWriteTime
_umask, _umask_s	Set default permission mask for new files created by program	System::IO::File::SetAttributes
_unlink, _wunlink	Delete file	System::IO::File::Delete

The following routines open files.

File-Handling Routines (Open File)

Routine	Use	.NET Framework equivalent
fopen, _wfopen, fopen_s, _wfopen_s	Opens a file and returns a pointer to the open file.	System::IO::File::Open, System::IO::FileStream::FileStream
_fsopen, _wfsopen	Open a stream with file sharing and returns a pointer to the open file.	System::IO::File::Open, System::IO::FileStream::FileStream
_open, _wopen	Opens a file and returns a file descriptor to the opened file.	System::IO::File::Open, System::IO::FileStream::FileStream
_sopen, _wsopen, _sopen_s, _wsopen_s	Open a file with file sharing and returns a file descriptor to the open file.
_pipe	Creates a pipe for reading and writing.	Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
freopen, _wfreopen, freopen_s, _wfreopen_s	Reassign a file pointer.	System::IO::File::Open, System::IO::FileStream::FileStream

The following functions provide a way to change the representation of the file between a FILE structure, a file descriptor, and a Win32 file handle.

_fdopen, _wfdopen	Associates a stream with a file that was previously opened for low-level I/O and returns a pointer to the open stream.	System::IO::FileStream::FileStream
_fileno	Gets the file descriptor associated with a stream.	System::IO::FileStream::Handle
_get_osfhandle	Return operating-system file handle associated with existing C run-time file descriptor	Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_open_osfhandle	Associates C run-time file descriptor with an existing operating-system file handle.	System::IO::FileStream::Handle

The following Win32 functions also open files and pipes:

• CreateFile

• CreatePipe

• CreateNamedPipe

See Also

Reference

Run-Time Routines by Category

Directory Control

System Calls