islower (original) (raw)

The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.

A newer edition of this document exists here

NAME

islower - test for a lowercase letter

SYNOPSIS

`#include <ctype.h>

int islower(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 islower() function shall test whether c is a character of class lower in the program's current locale; see the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 7, Locale.

The c argument is an int, the value of which the application shall ensure is a character representable as anunsigned char or equal to the value of the macro EOF. If the argument has any other value, the behavior is undefined.

RETURN VALUE

The islower() function shall return non-zero if c is a lowercase letter; otherwise, it shall return 0.

ERRORS

No errors are defined.

The following sections are informative.

EXAMPLES

Testing for a Lowercase Letter

The following example tests whether the value is a lowercase letter, based on the locale of the user, then uses it as part of a key value.

#include <ctype.h> #include <stdlib.h> #include <locale.h> ... char *keystr; int elementlen, len; char c; ... setlocale(LC_ALL, ""); ... len = 0; while (len < elementlen) { c = (char) (rand() % 256); ... if (islower(c)) keystr[len++] = c; } ...

APPLICATION USAGE

To ensure applications portability, especially across natural languages, only this function and those listed in the SEE ALSO section should be used for character classification.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

isalnum(), isalpha(), iscntrl(), isdigit(), isgraph(),isprint(), ispunct(), isspace(), isupper(), isxdigit(),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

The DESCRIPTION is updated to avoid use of the term "must" for application requirements.

An example is added.

End of informative text.

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