setmaxstdio.md

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Learn more about: _setmaxstdio	_setmaxstdio	05/21/2019	_setmaxstdio	msvcrt.dll msvcr80.dll msvcr90.dll msvcr100.dll msvcr100_clr0400.dll msvcr110.dll msvcr110_clr0400.dll msvcr120.dll msvcr120_clr0400.dll ucrtbase.dll api-ms-win-crt-stdio-l1-1-0.dll	DLLExport	apiref	setmaxstdio _setmaxstdio	maximum open files _setmaxstdio function setmaxstdio function open files, maximum

_setmaxstdio

Sets a maximum for the number of simultaneously open files at the stream I/O level.

Syntax

int _setmaxstdio(
   int new_max
);

Parameters

new_max
New maximum for the number of simultaneously open files at the stream I/O level.

Return value

Returns new_max if successful; -1 otherwise.

If new_max is less than _IOB_ENTRIES, or greater than the maximum number of handles available in the operating system, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, this function returns -1 and sets errno to EINVAL.

For information about these and other error codes, see errno, _doserrno, _sys_errlist, and _sys_nerr.

Remarks

The _setmaxstdio function changes the maximum value for the number of files that may be open simultaneously at the stream I/O level.

C run-time I/O now supports up to 8,192 files open simultaneously at the low I/O level. This level includes files opened and accessed using the _open, _read, and _write family of I/O functions. By default, up to 512 files can be open simultaneously at the stream I/O level. This level includes files opened and accessed using the fopen, fgetc, and fputc family of functions. The limit of 512 open files at the stream I/O level can be increased to a maximum of 8,192 by use of the _setmaxstdio function.

Because stream I/O-level functions, such as fopen, are built on top of the low I/O-level functions, the maximum of 8,192 is a hard upper limit for the number of simultaneously open files accessed through the C run-time library.

Note

This upper limit might be beyond what's supported by a particular Win32 platform and configuration.

Requirements

Routine	Required header
_setmaxstdio	<stdio.h>

For more compatibility information, see Compatibility.

Example

See _getmaxstdio for an example of using _setmaxstdio.

See also

Stream I/O