The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### 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.1-2008 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.

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

> None.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> setlocale, uselocale

> XBD 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.

End of informative text.

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