ISLOWER(3P) POSIX Programmer's Manual ISLOWER(3P)
PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond-
ing 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.
SEE ALSO
isalnum(), isalpha(), iscntrl(), isdigit(), isgraph(), isprint(), ispunct(), isspace(), isupper(), isxdigit(), setlocale(), the Base Defi-
nitions 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 Technol-
ogy -- 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 .
IEEE
/The Open Group 2003 ISLOWER(3P)