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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 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 behav-
       ior is undefined.
RETURN VALUE
       The  islower()  function shall return non-zero if c is a lowercase let-
       ter; 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 lan-
       guages, 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 Def-
       initions 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 .

IEEE/The Open Group                  2003                          ISLOWER(3P)