btowc

C

Language

Headers

Type support

Program utilities

Variadic function support

Error handling

Dynamic memory management

Date and time utilities

Strings library

Algorithms

Numerics

Input/output support

Localization support

Atomic operations (C11)

Thread support (C11)

Technical Specifications

Strings library

Byte strings

Multibyte strings

Wide strings

Null-terminated multibyte strings

Wide/multibyte conversions
mbsinit (C95)
mbtowc mbstowcsmbstowcs_s (C11) btowc (C95) mbrtowc (C95) mbsrtowcsmbsrtowcs_s (C95)(C11) mbrtoc16 (C11) c16rtomb (C11) c32rtomb (C11) mbrtoc32 (C11)	mblen wctombwctomb_s (C11) wcstombswcstombs_s (C11) wctob (C95) wcrtombwcrtomb_s (C95)(C11) wcsrtombswcsrtombs_s (C95)(C11) mbrlen (C95)
Types
mbstate_t (C95)

Defined in header <wchar.h>
wint_t btowc( int c );		(since C95)

Widens a single-byte character c (reinterpreted as unsigned char) to its wide character equivalent.

Most multibyte character encodings use single-byte codes to represent the characters from the ASCII character set. This function may be used to convert such characters to wchar_t.

Parameters

c

-

single-byte character to widen

Return value

WEOF if c is EOF

wide character representation of c if (unsigned char)c is a valid single-byte character in the initial shift state, WEOF otherwise.

Example

Run this code

#include <stdio.h>
#include <wchar.h>
#include <locale.h>
#include <assert.h>

void try_widen(unsigned char c)
{
    wint_t w = btowc(c);
    if(w != WEOF)
        printf("The single-byte character%#x widens to%#x\n", c, w);
    else
        printf("The single-byte character%#x failed to widen\n", c);
}

int main(void)
{
    char *loc = setlocale(LC_ALL, "lt_LT.iso88594");
    assert(loc);
    printf("In Lithuanian ISO-8859-4 locale:\n");
    try_widen('A');
    try_widen('\xdf'); // German letter  (U+00df) in ISO-8859-4
    try_widen('\xf9'); // Lithuanian letter  (U+0173) in ISO-8859-4

    setlocale(LC_ALL, "lt_LT.utf8");
    printf("In Lithuanian UTF-8 locale:\n");
    try_widen('A');
    try_widen('\xdf');
    try_widen('\xf9');
}

Possible output:

In Lithuanian ISO-8859-4 locale:
The single-byte character 0x41 widens to 0x41
The single-byte character 0xdf widens to 0xdf
The single-byte character 0xf9 widens to 0x173
In Lithuanian UTF-8 locale:
The single-byte character 0x41 widens to 0x41
The single-byte character 0xdf failed to widen
The single-byte character 0xf9 failed to widen

References

• C11 standard (ISO/IEC 9899:2011):

• 7.29.6.1.1 The btowc function (p: 441)

• C99 standard (ISO/IEC 9899:1999):

• 7.24.6.1.1 The btowc function (p: 387)

See also

wctob (C95)

narrows a wide character to a single-byte narrow character, if possible (function)