The Open Group Base Specifications Issue 6
IEEE Std 1003.1-2001
Copyright © 2001 The IEEE and The Open Group, All Rights reserved.

NAME

tolower - transliterate uppercase characters to lowercase

SYNOPSIS

#include <ctype.h>

int tolower(int c);

DESCRIPTION

[CX] [Option Start] 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 IEEE Std 1003.1-2001 defers to the ISO C standard. [Option End]

The tolower() function has 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() represents an uppercase letter, and there exists a corresponding lowercase letter [CX] [Option Start]  (as defined by character type information in the program locale category LC_CTYPE ), [Option End] the result shall be the corresponding lowercase letter. All other arguments in the domain are returned unchanged.

RETURN VALUE

Upon successful completion, tolower() shall return the lowercase letter corresponding to the argument passed; otherwise, it 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() , the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 7, Locale, <ctype.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.

End of informative text.
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