man islower () - test for a lowercase letter

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.

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>

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 .