ungetc-nolock-ungetwc-nolock.md

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_ungetc_nolock, _ungetwc_nolock	Learn more about: _ungetc_nolock, _ungetwc_nolock	4/2/2020	_ungetwc_nolock _ungetc_nolock _o__ungetc_nolock _o__ungetwc_nolock	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	STDIO/_ungetc_nolock CORECRT_WSTDIO/_ungetwc_nolock TCHAR/_ungettc_nolock _ungetc_nolock _ungetwc_nolock _ungettc_nolock	_ungettc_nolock function _ungetwc_nolock function characters, pushing back onto stream _ungetc_nolock function ungetwc_nolock function ungettc_nolock function ungetc_nolock function

_ungetc_nolock, _ungetwc_nolock

Pushes a character back onto the stream without locking.

Syntax

int _ungetc_nolock(
   int c,
   FILE *stream
);
wint_t _ungetwc_nolock(
   wint_t c,
   FILE *stream
);

Parameters

c
Character to be pushed.

stream
Pointer to FILE structure.

Return value

If successful, each of these functions returns the character argument c. If c can't be pushed back or if no character has been read, the input stream is unchanged and _ungetc_nolock returns EOF; _ungetwc_nolock returns WEOF. If stream is NULL, EOF or WEOF is returned, and errno is set to EINVAL.

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

Remarks

These functions are non-locking versions of ungetc and ungetwc. The versions with the _nolock suffix are identical except that they aren't protected from interference by other threads. They may be faster since they don't incur the overhead of locking out other threads. Use these functions only in thread-safe contexts such as single-threaded applications or where the calling scope already handles thread isolation.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Generic-text routine mappings

TCHAR.H routine	_UNICODE and _MBCS not defined	_MBCS defined	_UNICODE defined
_ungettc_nolock	_ungetc_nolock	_ungetc_nolock	_ungetwc_nolock

Requirements

Routine	Required header
_ungetc_nolock	<stdio.h>
_ungetwc_nolock	<stdio.h> or <wchar.h>

For more compatibility information, see Compatibility.

See also

Stream I/O
getc, getwc
putc, putwc