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_ungetc_nolock, _ungetwc_nolock

Pushes a character back onto the stream.

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


Character to be pushed.


Pointer to FILE structure.

If successful, each of these functions returns the character argument c. If c cannot 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 _doserrno, errno, _sys_errlist, and _sys_nerr.

These functions are non-locking versions of ungetc and ungetwc. The versions with the _nolock suffix are identical except that they are not protected from interference by other threads. They may be faster since they do not 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.

Generic-Text Routine Mappings

TCHAR.H routine

_UNICODE & _MBCS not defined

_MBCS defined

_UNICODE defined






Required header




<stdio.h> or <wchar.h>

For additional compatibility information, see Compatibility in the Introduction.

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.