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 (con-
       sult 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.

SEE ALSO
       isalnum(),  isalpha(),  iscntrl(),  isdigit(),  isgraph(), isprint(), ispunct(), isspace(), isupper(), isxdigit(), setlo-
       cale(), 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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                   ISLOWER(3P)