1ISLOWER(3P)                POSIX Programmer's Manual               ISLOWER(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       islower - test for a lowercase letter
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SYNOPSIS

15       #include <ctype.h>
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17       int islower(int c);
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DESCRIPTION

21       The islower() function shall test whether c is  a  character  of  class
22       lower  in the program's current locale; see the Base Definitions volume
23       of IEEE Std 1003.1-2001, Chapter 7, Locale.
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25       The c argument is an int, the value  of  which  the  application  shall
26       ensure is a character representable as an unsigned char or equal to the
27       value of the macro EOF. If the argument has any other value, the behav‐
28       ior is undefined.
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RETURN VALUE

31       The  islower()  function shall return non-zero if c is a lowercase let‐
32       ter; otherwise, it shall return 0.
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ERRORS

35       No errors are defined.
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37       The following sections are informative.
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EXAMPLES

40   Testing for a Lowercase Letter
41       The following example tests whether the value is  a  lowercase  letter,
42       based on the locale of the user, then uses it as part of a key value.
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45              #include <ctype.h>
46              #include <stdlib.h>
47              #include <locale.h>
48              ...
49              char *keystr;
50              int elementlen, len;
51              char c;
52              ...
53              setlocale(LC_ALL, "");
54              ...
55              len = 0;
56              while (len < elementlen) {
57                  c = (char) (rand() % 256);
58              ...
59                  if (islower(c))
60                      keystr[len++] = c;
61                  }
62              ...
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APPLICATION USAGE

65       To  ensure  applications  portability,  especially  across natural lan‐
66       guages, only this function and those listed in  the  SEE  ALSO  section
67       should be used for character classification.
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RATIONALE

70       None.
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FUTURE DIRECTIONS

73       None.
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SEE ALSO

76       isalnum(),   isalpha(),  iscntrl(),  isdigit(),  isgraph(),  isprint(),
77       ispunct(), isspace(), isupper(), isxdigit(), setlocale(), the Base Def‐
78       initions volume of IEEE Std 1003.1-2001, Chapter 7, Locale, <ctype.h>
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81       Portions  of  this text are reprinted and reproduced in electronic form
82       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
83       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
84       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
85       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
86       event of any discrepancy between this version and the original IEEE and
87       The  Open Group Standard, the original IEEE and The Open Group Standard
88       is the referee document. The original Standard can be  obtained  online
89       at http://www.opengroup.org/unix/online.html .
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93IEEE/The Open Group                  2003                          ISLOWER(3P)
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