ungetwc(3p) — Linux manual page


UNGETWC(3P)               POSIX Programmer's Manual              UNGETWC(3P)

PROLOG         top

       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.

NAME         top

       ungetwc — push wide-character code back into the input stream

SYNOPSIS         top

       #include <stdio.h>
       #include <wchar.h>

       wint_t ungetwc(wint_t wc, FILE *stream);

DESCRIPTION         top

       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.1‐2008 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

       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

       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.

RETURN VALUE         top

       Upon successful completion, ungetwc() shall return the wide-character
       code corresponding to the pushed-back character. Otherwise, it shall
       return WEOF.

ERRORS         top

       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         top




RATIONALE         top




SEE ALSO         top

       Section 2.5, Standard I/O Streams, fseek(3p), fsetpos(3p), read(3p),
       rewind(3p), setbuf(3p)

       The Base Definitions volume of POSIX.1‐2008, stdio.h(0p), wchar.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/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                 2013                         UNGETWC(3P)

Pages that refer to this page: wchar.h(0p)