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.TH FWIDE 3  2016-03-15 "GNU" "Linux Programmer's Manual"

.SH NAME

fwide \- set and determine the orientation of a FILE stream

.SH SYNOPSIS

.nf

.B #include <wchar.h>

.PP

.BI "int fwide(FILE *" stream ", int " mode );

.fi

.PP

.in -4n

Feature Test Macro Requirements for glibc (see

.BR feature_test_macros (7)):

.in

.ad l

.PP

.BR fwide ():

.RS 4

_XOPEN_SOURCE\ >=\ 500 || _ISOC99_SOURCE ||

.br

_POSIX_C_SOURCE\ >=\ 200112L

.RE

.ad

.SH DESCRIPTION

When \fImode\fP is zero, the

.BR fwide ()

function determines the current

orientation of \fIstream\fP.

It returns a positive value if \fIstream\fP is

wide-character oriented, that is, if wide-character I/O is permitted but char

I/O is disallowed.

It returns a negative value if \fIstream\fP is byte oriented\(emthat is,

if char I/O is permitted but wide-character I/O is disallowed.

It

returns zero if \fIstream\fP has no orientation yet; in this case the next

I/O operation might change the orientation (to byte oriented if it is a char

I/O operation, or to wide-character oriented if it is a wide-character I/O

operation).

.PP

Once a stream has an orientation, it cannot be changed and persists until

the stream is closed.

.PP

When \fImode\fP is nonzero, the

.BR fwide ()

function first attempts to set

\fIstream\fP's orientation (to wide-character oriented

if \fImode\fP is greater than 0, or

to byte oriented if \fImode\fP is less than 0).

It then returns a value denoting the

current orientation, as above.

.SH RETURN VALUE

The

.BR fwide ()

function returns the stream's orientation, after possibly

changing it.

A positive return value means wide-character oriented.

A negative return value means byte oriented.

A return value of zero means undecided.

.SH CONFORMING TO

POSIX.1-2001, POSIX.1-2008, C99.

.SH NOTES

Wide-character output to a byte oriented stream can be performed through the

.BR fprintf (3)

function with the

.B %lc

and

.B %ls

directives.

.PP

Char oriented output to a wide-character oriented stream can be performed

through the

.BR fwprintf (3)

function with the

.B %c

and

.B %s

directives.

.SH SEE ALSO

.BR fprintf (3),

.BR fwprintf (3)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I man-pages

project.

A description of the project,

information about reporting bugs,

and the latest version of this page,

can be found at

\%https://www.kernel.org/doc/man\-pages/.