stdio/FreeBSD/ungetwc.3

   1 .\"     $NetBSD: ungetwc.3,v 1.3 2002/02/07 07:00:27 ross Exp $
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   7 .\" Chris Torek and the American National Standards Committee X3,
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  34 .\"     @(#)ungetc.3    8.1 (Berkeley) 6/4/93
  35 .\" $FreeBSD: src/lib/libc/stdio/ungetwc.3,v 1.6 2007/01/09 00:28:07 imp Exp $
  36 .\"
  37 .Dd March 3, 2004
  38 .Dt UNGETWC 3
  39 .Os
  40 .Sh NAME
  41 .Nm ungetwc ,
  42 .Nm ungetwc_l
  43 .Nd un-get wide character from input stream
  44 .Sh LIBRARY
  45 .Lb libc
  46 .Sh SYNOPSIS
  47 .In stdio.h
  48 .In wchar.h
  49 .Ft wint_t
  50 .Fo ungetwc
  51 .Fa "wint_t wc"
  52 .Fa "FILE *stream"
  53 .Fc
  54 .In stdio.h
  55 .In wchar.h
  56 .In xlocale.h
  57 .Ft wint_t
  58 .Fo ungetwc_l
  59 .Fa "wint_t wc"
  60 .Fa "FILE *stream"
  61 .Fa "locale_t loc"
  62 .Fc
  63 .Sh DESCRIPTION
  64 The
  65 .Fn ungetwc
  66 function pushes the wide character
  67 .Fa wc
  68 (converted to an
  69 .Vt wchar_t )
  70 back onto the input stream pointed to by
  71 .Fa stream .
  72 The pushed-backed wide characters will be returned (in reverse order)
  73 by subsequent reads on the stream.
  74 A successful intervening call to one of the file
  75 positioning functions
  76 .Xr fseek 3 ,
  77 .Xr fsetpos 3 ,
  78 or
  79 .Xr rewind 3 ,
  80 using the same stream,
  81 will discard the pushed-back wide characters.
  82 .Pp
  83 Only one wide character of push-back is guaranteed,
  84 but as long as there is sufficient memory,
  85 an effectively infinite amount of push-back is allowed.
  86 .Pp
  87 If a character is successfully pushed-back,
  88 the end-of-file indicator for the stream is cleared.
  89 .Pp
  90 Although the
  91 .Fn ungetwc
  92 function uses the current locale, the
  93 .Fn ungetwc_l
  94 function may be passed a locale directly. See
  95 .Xr xlocale 3
  96 for more information.
  97 .Sh RETURN VALUES
  98 The
  99 .Fn ungetwc
 100 function
 101 returns
 102 the wide character pushed-back after the conversion, or
 103 .Dv WEOF
 104 if the operation fails.
 105 If the value of the argument
 106 .Fa c
 107 character equals
 108 .Dv WEOF ,
 109 the operation will fail and the stream will remain unchanged.
 110 .Sh SEE ALSO
 111 .Xr fseek 3 ,
 112 .Xr getwc 3 ,
 113 .Xr xlocale 3
 114 .Sh STANDARDS
 115 The
 116 .Fn ungetwc
 117 function conforms to
 118 .St -isoC-99 .