NAME

tolower, tolower_l — transliterate uppercase characters to lowercase

SYNOPSIS

#include <ctype.h>

int tolower(int c);


[CX] int tolower_l(int c, locale_t locale);

DESCRIPTION

For tolower(): ^[CX]  The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2024 defers to the ISO C standard.

The tolower() ^[CX]  and tolower_l()  functions have as a domain a type int, the value of which is representable as an unsigned char or the value of EOF. If the argument has any other value, the behavior is undefined. If the argument of tolower() ^[CX]  or tolower_l()  represents an uppercase letter, and there exists a corresponding lowercase letter as defined by character type information in the current locale ^[CX]  or in the locale represented by locale,  respectively (category LC_CTYPE ), the result shall be the corresponding lowercase letter. All other arguments in the domain are returned unchanged.

^[CX] The behavior is undefined if the locale argument to tolower_l() is the special locale object LC_GLOBAL_LOCALE or is not a valid locale object handle.

RETURN VALUE

Upon successful completion, the tolower() ^[CX]  and tolower_l()  functions shall return the lowercase letter corresponding to the argument passed; otherwise, they shall return the argument unchanged.

ERRORS

No errors are defined.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

setlocale, uselocale

XBD 7. Locale, <ctype.h>, <locale.h>

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 6

Extensions beyond the ISO C standard are marked.

Issue 7

The tolower_l() function is added from The Open Group Technical Standard, 2006, Extended API Set Part 4.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0671 [283] and XSH/TC1-2008/0672 [283] are applied.