stdio/FreeBSD/fflush.3

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  32 .\"     @(#)fflush.3    8.1 (Berkeley) 6/4/93
  33 .\" $FreeBSD: src/lib/libc/stdio/fflush.3,v 1.11 2007/01/09 00:28:06 imp Exp $
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  35 .Dd August 1, 2019
  36 .Dt FFLUSH 3
  37 .Os
  38 .Sh NAME
  39 .Nm fflush ,
  40 .Nm fpurge
  41 .Nd flush a stream
  42 .Sh LIBRARY
  43 .Lb libc
  44 .Sh SYNOPSIS
  45 .In stdio.h
  46 .Ft int
  47 .Fn fflush "FILE *stream"
  48 .Ft int
  49 .Fn fpurge "FILE *stream"
  50 .Sh DESCRIPTION
  51 The function
  52 .Fn fflush
  53 synchronizes the state of the given
  54 .Fa stream
  55 in light of buffered I/O.
  56 For output or update streams it writes all buffered data via the stream's
  57 underlying write function.
  58 For input streams it seeks to the current file position indicator via the
  59 stream's underlying seek function.
  60 The open status of the stream is unaffected.
  61 .Pp
  62 If the
  63 .Fa stream
  64 argument is
  65 .Dv NULL ,
  66 .Fn fflush
  67 flushes
  68 .Em all
  69 open streams.
  70 .Pp
  71 The function
  72 .Fn fpurge
  73 erases any input or output buffered in the given
  74 .Fa stream .
  75 For output streams this discards any unwritten output.
  76 For input streams this discards any input read from the underlying object
  77 but not yet obtained via
  78 .Xr getc 3 ;
  79 this includes any text pushed back via
  80 .Xr ungetc 3 .
  81 .Sh RETURN VALUES
  82 Upon successful completion 0 is returned.
  83 Otherwise,
  84 .Dv EOF
  85 is returned and the global variable
  86 .Va errno
  87 is set to indicate the error.
  88 .Sh ERRORS
  89 .Bl -tag -width Er
  90 .It Bq Er EBADF
  91 The
  92 .Fa stream
  93 argument
  94 is not an open stream.
  95 .El
  96 .Pp
  97 The function
  98 .Fn fflush
  99 may also fail and set
 100 .Va errno
 101 for any of the errors specified for the routines
 102 .Xr write 2
 103 and
 104 .Xr lseek 2 .
 105 .Sh SEE ALSO
 106 .Xr write 2 ,
 107 .Xr fclose 3 ,
 108 .Xr fopen 3 ,
 109 .Xr lseek 2 ,
 110 .Xr setbuf 3
 111 .Sh STANDARDS
 112 The
 113 .Fn fflush
 114 function
 115 conforms to
 116 .St -isoC
 117 and
 118 .St -susv3 .