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NAME
ungetwc - push wide-character code back into the input stream
SYNOPSIS
#include <stdio.h> #include <wchar.h> wint_t ungetwc(wint_t wc, FILE *stream);
DESCRIPTION
The ungetwc() function shall push the character corresponding to the wide-character code specified by wc
back onto the input stream pointed to by stream. The pushed-back characters shall be returned by
subsequent reads on that stream in the reverse order of their pushing. A successful intervening call
(with the stream pointed to by stream) to a file-positioning function ( fseek(), fsetpos(), or rewind())
discards any pushed-back characters for the stream. The external storage corresponding to the stream is
unchanged.
At least one character of push-back shall be provided. If ungetwc() is called too many times on the same
stream without an intervening read or file-positioning operation on that stream, the operation may fail.
If the value of wc equals that of the macro WEOF, the operation shall fail and the input stream shall be
left unchanged.
A successful call to ungetwc() shall clear the end-of-file indicator for the stream. The value of the
file-position indicator for the stream after reading or discarding all pushed-back characters shall be
the same as it was before the characters were pushed back. The file-position indicator is decremented (by
one or more) by each successful call to ungetwc(); if its value was 0 before a call, its value is
unspecified after the call.
RETURN VALUE
Upon successful completion, ungetwc() shall return the wide-character code corresponding to the pushed-
back character. Otherwise, it shall return WEOF.
ERRORS
The ungetwc() function may fail if:
EILSEQ An invalid character sequence is detected, or a wide-character code does not correspond to a valid
character.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
fseek() , fsetpos() , read() , rewind() , setbuf() , the Base Definitions volume of IEEE Std 1003.1-2001,
<stdio.h>, <wchar.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The
original Standard can be obtained online at http://www.opengroup.org/unix/online.html .