towlower

Defined in header `<wctype.h>`
wint_t towlower( wint_t wc );		(since C95)

Converts the given wide character to lowercase, if possible.

Parameters

wc

-

wide character to be converted

Return value

Lowercase version of wc or unmodified wc if no lowercase version is listed in the current C locale.

Notes

Only 1:1 character mapping can be performed by this function, e.g. the Greek uppercase letter 'Σ' has two lowercase forms, depending on the position in a word: 'σ' and 'ς'. A call to towlower cannot be used to obtain the correct lowercase form in this case.

ISO 30112 specifies which pairs of Unicode characters are included in this mapping.

Example

Run this code

#include <locale.h>
#include <stdio.h>
#include <wchar.h>
#include <wctype.h>
 
int main(void)
{
    wchar_t wc = L'\u0190'; // Latin capital open E ('Ɛ')
    printf("in the default locale, towlower(%#x) = %#x\n", wc, towlower(wc));
    setlocale(LC_ALL, "en_US.utf8");
    printf("in Unicode locale, towlower(%#x) = %#x\n", wc, towlower(wc));
}

Output:

in the default locale, towlower(0x190) = 0x190
in Unicode locale, towlower(0x190) = 0x25b

References

C23 standard (ISO/IEC 9899:2023):

7.30.3.1.1 The towlower function (p: TBD)

C17 standard (ISO/IEC 9899:2018):

7.30.3.1.1 The towlower function (p: TBD)

C11 standard (ISO/IEC 9899:2011):

7.30.3.1.1 The towlower function (p: 453)

C99 standard (ISO/IEC 9899:1999):

7.25.3.1.1 The towlower function (p: 399)

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Technical Specifications
Symbol index

towupper (C95)	converts a wide character to uppercase (function)
tolower	converts a character to lowercase (function)