stdio/ungetwc.3

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  38 .\"     @(#)ungetc.3    8.1 (Berkeley) 6/4/93
  39 .\" $FreeBSD: src/lib/libc/stdio/ungetwc.3,v 1.5 2004/03/16 13:30:11 tjr Exp $
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  41 .Dd March 3, 2004
  42 .Dt UNGETWC 3
  43 .Os
  44 .Sh NAME
  45 .Nm ungetwc ,
  46 .Nm ungetwc_l
  47 .Nd un-get wide character from input stream
  48 .Sh LIBRARY
  49 .Lb libc
  50 .Sh SYNOPSIS
  51 .In stdio.h
  52 .In wchar.h
  53 .Ft wint_t
  54 .Fo ungetwc
  55 .Fa "wint_t wc"
  56 .Fa "FILE *stream"
  57 .Fc
  58 .In stdio.h
  59 .In wchar.h
  60 .In xlocale.h
  61 .Ft wint_t
  62 .Fo ungetwc_l
  63 .Fa "wint_t wc"
  64 .Fa "FILE *stream"
  65 .Fa "locale_t loc"
  66 .Fc
  67 .Sh DESCRIPTION
  68 The
  69 .Fn ungetwc
  70 function pushes the wide character
  71 .Fa wc
  72 (converted to an
  73 .Vt wchar_t )
  74 back onto the input stream pointed to by
  75 .Fa stream .
  76 The pushed-backed wide characters will be returned (in reverse order)
  77 by subsequent reads on the stream.
  78 A successful intervening call to one of the file
  79 positioning functions
  80 .Xr fseek 3 ,
  81 .Xr fsetpos 3 ,
  82 or
  83 .Xr rewind 3 ,
  84 using the same stream,
  85 will discard the pushed-back wide characters.
  86 .Pp
  87 Only one wide character of push-back is guaranteed,
  88 but as long as there is sufficient memory,
  89 an effectively infinite amount of push-back is allowed.
  90 .Pp
  91 If a character is successfully pushed-back,
  92 the end-of-file indicator for the stream is cleared.
  93 .Pp
  94 Although the
  95 .Fn ungetwc
  96 function uses the current locale, the
  97 .Fn ungetwc_l
  98 function may be passed a locale directly. See
  99 .Xr xlocale 3
 100 for more information.
 101 .Sh RETURN VALUES
 102 The
 103 .Fn ungetwc
 104 function
 105 returns
 106 the wide character pushed-back after the conversion, or
 107 .Dv WEOF
 108 if the operation fails.
 109 If the value of the argument
 110 .Fa c
 111 character equals
 112 .Dv WEOF ,
 113 the operation will fail and the stream will remain unchanged.
 114 .Sh SEE ALSO
 115 .Xr fseek 3 ,
 116 .Xr getwc 3 ,
 117 .Xr xlocale 3
 118 .Sh STANDARDS
 119 The
 120 .Fn ungetwc
 121 function conforms to
 122 .St -isoC-99 .