File Handling

Visual Studio 6.0

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

The C run-time libraries have a preset limit for the number of files that can be open at any one time. The limit for applications that link with the single-thread static library (LIBC.LIB) is 64 file handles or 20 file streams. Applications that link with either the static or dynamic multithread library (LIBCMT.LIB or MSVCRT.LIB and MSVCRT.DLL), have a limit of 256 file handles or 40 file streams. Attempting to open more than the maximum number of file handles or file streams causes program failure.

The following routines operate on files designated by a file handle:

File-Handling Routines (File Handle)

Routine Use
_chsize Change file size
_filelength Get file length
_fstat, _fstati64 Get file-status information on handle
_isatty Check for character device
_locking Lock areas of file
_setmode Set file-translation mode

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

File-Handling Routines (Path or Filename)

Routine Use
_access, _waccess Check file-permission setting
_chmod, _wchmod Change file-permission setting
_fullpath, _wfullpath Expand a relative path to its absolute path name
_get_osfhandle Return operating-system file handle associated with existing stream FILE pointer
_makepath, _wmakepath Merge path components into single, full path
_mktemp, _wmktemp Create unique filename
_open_osfhandle Associate C run-time file handle with existing operating-system file handle
remove, _wremove Delete file
rename, _wrename Rename file
_splitpath, _wsplitpath Parse path into components
_stat, _stati64, _wstat, _wstati64 Get file-status information on named file
_umask Set default permission mask for new files created by program
_unlink, _wunlink Delete file