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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 dif-
       fer (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.

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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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)