man3/stdio_ext.3

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  25 .TH STDIO_EXT 3 2015-03-02 "" "Linux Programmer's Manual"
  26 .SH NAME
  27 __fbufsize, __flbf, __fpending, __fpurge, __freadable,
  28 __freading, __fsetlocking, __fwritable, __fwriting, _flushlbf \-
  29 interfaces to stdio FILE structure
  30 .SH SYNOPSIS
  31 .nf
  32 .B #include <stdio.h>
  33 .B #include <stdio_ext.h>
  34 .PP
  35 .BI "size_t __fbufsize(FILE *" stream );
  36 .BI "size_t __fpending(FILE *" stream );
  37 .BI "int __flbf(FILE *" stream );
  38 .BI "int __freadable(FILE *" stream );
  39 .BI "int __fwritable(FILE *" stream );
  40 .BI "int __freading(FILE *" stream );
  41 .BI "int __fwriting(FILE *" stream );
  42 .BI "int __fsetlocking(FILE *" stream ", int " type );
  43 .B "void _flushlbf(void);"
  44 .BI "void __fpurge(FILE *" stream );
  45 .fi
  46 .SH DESCRIPTION
  47 Solaris introduced routines to allow portable access to the
  48 internals of the
  49 .I FILE
  50 structure, and glibc also implemented these.
  51 .PP
  52 The
  53 .BR __fbufsize ()
  54 function returns the size of the buffer currently used
  55 by the given stream.
  56 .PP
  57 The
  58 .BR __fpending ()
  59 function returns the number of bytes in the output buffer.
  60 For wide-oriented streams the unit is wide characters.
  61 This function is undefined on buffers in reading mode,
  62 or opened read-only.
  63 .PP
  64 The
  65 .BR __flbf ()
  66 function returns a nonzero value if the stream is line-buffered,
  67 and zero otherwise.
  68 .PP
  69 The
  70 .BR __freadable ()
  71 function returns a nonzero value if the stream allows reading,
  72 and zero otherwise.
  73 .PP
  74 The
  75 .BR __fwritable ()
  76 function returns a nonzero value if the stream allows writing,
  77 and zero otherwise.
  78 .PP
  79 The
  80 .BR __freading ()
  81 function returns a nonzero value if the stream is read-only, or
  82 if the last operation on the stream was a read operation,
  83 and zero otherwise.
  84 .PP
  85 The
  86 .BR __fwriting ()
  87 function returns a nonzero value if the stream is write-only (or
  88 append-only), or if the last operation on the stream was a write
  89 operation, and zero otherwise.
  90 .PP
  91 The
  92 .BR __fsetlocking ()
  93 function can be used to select the desired type of locking on the stream.
  94 It returns the current type.
  95 The
  96 .I type
  97 argument can take the following three values:
  98 .TP
  99 .B FSETLOCKING_INTERNAL
 100 Perform implicit locking around every operation on the given stream
 101 (except for the *_unlocked ones).
 102 This is the default.
 103 .TP
 104 .B FSETLOCKING_BYCALLER
 105 The caller will take care of the locking (possibly using
 106 .BR flockfile (3)
 107 in case there is more than one thread), and the stdio routines
 108 will not do locking until the state is reset to
 109 .BR FSETLOCKING_INTERNAL .
 110 .TP
 111 .B FSETLOCKING_QUERY
 112 Don't change the type of locking.
 113 (Only return it.)
 114 .PP
 115 The
 116 .BR _flushlbf ()
 117 function flushes all line-buffered streams.
 118 (Presumably so that
 119 output to a terminal is forced out, say before reading keyboard input.)
 120 .PP
 121 The
 122 .BR __fpurge ()
 123 function discards the contents of the stream's buffer.
 124 .SH ATTRIBUTES
 125 For an explanation of the terms used in this section, see
 126 .BR attributes (7).
 127 .TS
 128 allbox;
 129 lbw28 lb lb
 130 l l l.
 131 Interface       Attribute       Value
 132 T{
 133 .BR __fbufsize (),
 134 .BR __fpending (),
 135 .br
 136 .BR __fpurge (),
 137 .BR __fsetlocking ()
 138 T}      Thread safety   MT-Safe race:stream
 139 T{
 140 .BR __flbf (),
 141 .BR __freadable (),
 142 .br
 143 .BR __freading (),
 144 .BR __fwritable (),
 145 .br
 146 .BR __fwriting (),
 147 .BR _flushlbf ()
 148 T}      Thread safety   MT-Safe
 149 .TE
 150 .SH SEE ALSO
 151 .BR flockfile (3),
 152 .BR fpurge (3)