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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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UNGETWC(3P) POSIX Programmer's Manual UNGETWC(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
ungetwc — push wide-character code back into the input stream
#include <stdio.h>
#include <wchar.h>
wint_t ungetwc(wint_t wc, FILE *stream);
The functionality described on this reference page is aligned
with the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
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(),
fseeko(), fsetpos(), or rewind()) or fflush() shall discard 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 all pushed-back characters have
been read, or discarded by calling fseek(), fseeko(), fsetpos(),
or rewind() (but not fflush()), 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.
Upon successful completion, ungetwc() shall return the wide-
character code corresponding to the pushed-back character.
Otherwise, it shall return WEOF.
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.
None.
None.
None.
None.
Section 2.5, Standard I/O Streams, fseek(3p), fsetpos(3p),
read(3p), rewind(3p), setbuf(3p)
The Base Definitions volume of POSIX.1‐2017, stdio.h(0p),
wchar.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 UNGETWC(3P)
Pages that refer to this page: wchar.h(0p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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