islower (3p) - Linux Manuals

islower: test for a lowercase letter

PROLOG

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

islower - test for a lowercase letter

SYNOPSIS

#include <ctype.h>

int islower(int c);

DESCRIPTION

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 an unsigned 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.

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .