__fbufsize(3c)

1__fbufsize(3C)           Standard C Library Functions           __fbufsize(3C)
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NAME

6       __fbufsize,  __flbf,  __fpending,  __fpurge,  __freadable,  __freading,
7       __fsetlocking, __fwritable, __fwriting, _flushlbf - interfaces to stdio
8       FILE structure
9

SYNOPSIS

11       #include <stdio.h>
12       #include <stdio_ext.h>
13
14       size_t __fbufsiz(FILE *stream);
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16
17       int __flbf(FILE *stream);
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19
20       size_t __fpending(FILE *stream);
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23       void __fpurge(FILE *stream);
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25
26       int __freadable(FILE *stream);
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29       int __freading(FILE *stream);
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31
32       int __fsetlocking(FILE *stream, int type);
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34
35       int __fwritable(FILE *stream);
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37
38       int __fwriting(FILE *stream);
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40
41       void _flushlbf(void);
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DESCRIPTION

45       These functions provide portable access to the members of the stdio(3C)
46       FILE structure.
47
48
49       The __fbufsize() function returns in bytes the size of the buffer  cur‐
50       rently in use by the given stream.
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52
53       The __flbf() function returns non-zero if the stream is line-buffered.
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55
56       The  __fpending  function returns in bytes the amount of output pending
57       on a stream.
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59
60       The __fpurge() function  discards  any  pending  buffered  I/O  on  the
61       stream.
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63
64       The  __freadable()  function returns non-zero if it is possible to read
65       from a stream.
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67
68       The __freading() function returns non-zero if the file  is  open  read‐
69       only,  or if the last operation on the stream was a read operation such
70       as fread(3C) or fgetc(3C). Otherwise it returns 0.
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72
73       The __fsetlocking() function allows the type of  locking  performed  by
74       stdio on a given stream to be controlled by the programmer.
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77       If type is FSETLOCKING_INTERNAL, stdio performs implicit locking around
78       every operation on the given stream.  This is the default system behav‐
79       ior on that stream.
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81
82       If  type  is  FSETLOCKING_BYCALLER,  stdio  assumes  that the caller is
83       responsible for maintaining the integrity of the stream in the face  of
84       access  by multiple threads.  If there is only one thread accessing the
85       stream, nothing further needs to be  done.   If  multiple  threads  are
86       accessing the stream, then the caller can use the flockfile(), funlock‐
87       file(), and ftrylockfile() functions  described  on  the  flockfile(3C)
88       manual  page  to  provide the appropriate locking. In both this and the
89       case where type is FSETLOCKING_INTERNAL,  __fsetlocking()  returns  the
90       previous state of the stream.
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93       If type is FSETLOCKING_QUERY, __fsetlocking() returns the current state
94       of the stream without changing it.
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96
97       The __fwritable() function returns non-zero if it is possible to  write
98       on a stream.
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100
101       The  __fwriting()  function returns non-zero if the file is open write-
102       only or append-only, or if the last operation on the stream was a write
103       operation such as fwrite(3C) or fputc(3C). Otherwise it returns 0.
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105
106       The  _flushlbf()  function flushes all line-buffered files.  It is used
107       when reading from a line-buffered file.
108

USAGE

110       Although the contents of the stdio FILE structure have always been pri‐
111       vate  to  the  stdio  implementation,  some applications have needed to
112       obtain information about a stdio stream that was not accessible through
113       a  supported  interface.  These applications have resorted to accessing
114       fields of the FILE structure directly, rendering them possibly non-por‐
115       table  to  new  implementations  of  stdio,  or more likely, preventing
116       enhancements to stdio that would cause those applications to break.
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118
119       In the 64-bit environment, the FILE structure is opaque.  The functions
120       described  here  are  provided  as a means of obtaining the information
121       that up to now has been retrieved directly  from  the  FILE  structure.
122       Because  they  are based on the needs of existing applications (such as
123       mh and emacs), they may be  extended  as  other  programs  are  ported.
124       Although  they  may  still  be non-portable to other operating systems,
125       they will be compatible from each Solaris release to the next.   Inter‐
126       faces that are more portable are under development.
127

ATTRIBUTES

129       See attributes(5) for descriptions of the following attributes:
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133
134       ┌─────────────────────────────┬─────────────────────────────┐
135       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
136       ├─────────────────────────────┼─────────────────────────────┤
137       │MT-Level                     │__fsetlocking()  is Unsafe;  │
138       │                             │all others are MT-Safe       │
139       ├─────────────────────────────┼─────────────────────────────┤
140       │Interface Stability          │Evolving                     │
141       └─────────────────────────────┴─────────────────────────────┘
142

NAME

SYNOPSIS

DESCRIPTION

USAGE

ATTRIBUTES

SEE ALSO