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ISLOWER(3P) POSIX Programmer's Manual ISLOWER(3P)
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.
islower, islower_l — test for a lowercase letter
#include <ctype.h>
int islower(int c);
int islower_l(int c, locale_t locale);
For islower(): The functionality described on this reference page is
aligned with the ISO C standard. Any conflict between the
requirements described here and the ISO C standard is unintentional.
This volume of POSIX.1‐2008 defers to the ISO C standard.
The islower() and islower_l() functions shall test whether c is a
character of class lower in the current locale, or in the locale
represented by locale, respectively; see the Base Definitions volume
of POSIX.1‐2008, 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.
The behavior is undefined if the locale argument to islower_l() is
the special locale object LC_GLOBAL_LOCALE or is not a valid locale
object handle.
The islower() and islower_l() functions shall return non-zero if c is
a lowercase letter; otherwise, they shall return 0.
No errors are defined.
The following sections are informative.
Testing for a Lowercase Letter
Two examples follow, the first using islower(), the second using
multiple concurrent locales and islower_l().
The examples test whether the value is a lowercase letter, based on
the current locale, then use it as part of a key value.
/* Example 1 -- using islower() */
#include <ctype.h>
#include <stdlib.h>
#include <locale.h>
...
char *keystr;
int elementlen, len;
unsigned char c;
...
setlocale(LC_ALL, "");
...
len = 0;
while (len < elementlen) {
c = (unsigned char) (rand() % 256);
...
if (islower(c))
keystr[len++] = c;
}
...
/* Example 2 -- using islower_l() */
#include <ctype.h>
#include <stdlib.h>
#include <locale.h>
...
char *keystr;
int elementlen, len;
unsigned char c;
...
locale_t loc = newlocale (LC_ALL_MASK, "", (locale_t) 0);
...
len = 0;
while (len < elementlen) {
c = (unsigned char) (rand() % 256);
...
if (islower_l(c, loc))
keystr[len++] = c;
}
...
To ensure applications portability, especially across natural
languages, only these functions and the functions in the reference
pages listed in the SEE ALSO section should be used for character
classification.
None.
None.
isalnum(3p), isalpha(3p), isblank(3p), iscntrl(3p), isdigit(3p),
isgraph(3p), isprint(3p), ispunct(3p), isspace(3p), isupper(3p),
isxdigit(3p), setlocale(3p), uselocale(3p)
The Base Definitions volume of POSIX.1‐2008, Chapter 7, Locale,
ctype.h(0p), locale.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 ISLOWER(3P)
Pages that refer to this page: ctype.h(0p), isalnum(3p), isalpha(3p), isblank(3p), iscntrl(3p), isdigit(3p), isgraph(3p), isprint(3p), ispunct(3p), isspace(3p), isupper(3p), isxdigit(3p), setlocale(3p), _toupper(3p)