fwide(3) - f38

1fwide(3)                   Library Functions Manual                   fwide(3)
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NAME

6       fwide - set and determine the orientation of a FILE stream
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <wchar.h>
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14       int fwide(FILE *stream, int mode);
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16   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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18       fwide():
19           _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE
20               || _POSIX_C_SOURCE >= 200112L
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DESCRIPTION

23       When mode is zero, the fwide() function determines the current orienta‐
24       tion of stream.  It returns a positive value if stream is  wide-charac‐
25       ter  oriented, that is, if wide-character I/O is permitted but char I/O
26       is disallowed.  It returns a negative value if stream is byte oriented—
27       that is, if char I/O is permitted but wide-character I/O is disallowed.
28       It returns zero if stream has no orientation yet; in this case the next
29       I/O operation might change the orientation (to byte oriented if it is a
30       char I/O operation, or to wide-character oriented if it is a wide-char‐
31       acter I/O operation).
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33       Once a stream has an orientation, it cannot be changed and persists un‐
34       til the stream is closed.
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36       When mode is nonzero,  the  fwide()  function  first  attempts  to  set
37       stream's  orientation  (to  wide-character  oriented if mode is greater
38       than 0, or to byte oriented if mode is less than 0).  It then returns a
39       value denoting the current orientation, as above.
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RETURN VALUE

42       The  fwide()  function returns the stream's orientation, after possibly
43       changing it.  A positive return value means wide-character oriented.  A
44       negative  return  value  means  byte  oriented.  A return value of zero
45       means undecided.
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STANDARDS

48       C11, POSIX.1-2008.
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HISTORY

51       POSIX.1-2001, C99.
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NOTES

54       Wide-character output to  a  byte  oriented  stream  can  be  performed
55       through the fprintf(3) function with the %lc and %ls directives.
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57       Char  oriented  output  to a wide-character oriented stream can be per‐
58       formed through the fwprintf(3) function with the %c and %s directives.
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