Namespaces
Variants
Actions

islower

From cppreference.com
< c‎ | string‎ | byte
 
 
 
Null-terminated byte strings
Functions
Character manipulation
Conversions to and from numeric formats
(C23)(C23)(C23)
String manipulation String examination Memory manipulation Miscellaneous
 
Defined in header <ctype.h>
int islower( int ch );

Checks if the given character is classified as a lowercase character according to the current C locale. In the default "C" locale, islower returns true only for the lowercase letters (abcdefghijklmnopqrstuvwxyz).

If islower returns true, it is guaranteed that iscntrl , isdigit , ispunct , and isspace return false for the same character in the same C locale.

The behavior is undefined if the value of ch is not representable as unsigned char and is not equal to EOF .

Contents

[edit] Parameters

ch - character to classify

[edit] Return value

Non-zero value if the character is a lowercase letter, zero otherwise.

[edit] Example

Run this code
#include <ctype.h>
#include <locale.h>
#include <stdio.h>
 
int main(void)
{
 unsigned char c = '\xe5'; // letter å in ISO-8859-1
 printf ("In the default C locale, \\xe5 is %slowercase\n",
 islower(c) ? "" : "not " );
 setlocale (LC_ALL, "en_GB.iso88591");
 printf ("In ISO-8859-1 locale, \\xe5 is %slowercase\n",
 islower(c) ? "" : "not " );
}

Possible output: 

In the default C locale, \xe5 is not lowercase
In ISO-8859-1 locale, \xe5 is lowercase

[edit] References

  • C23 standard (ISO/IEC 9899:2024):
  • 7.4.1.7 The islower function (p: TBD)
  • C17 standard (ISO/IEC 9899:2018):
  • 7.4.1.7 The islower function (p: 146)
  • C11 standard (ISO/IEC 9899:2011):
  • 7.4.1.7 The islower function (p: 202)
  • C99 standard (ISO/IEC 9899:1999):
  • 7.4.1.7 The islower function (p: 183)
  • C89/C90 standard (ISO/IEC 9899:1990):
  • 4.3.1.6 The islower function

[edit] See also

(C95)
checks if a wide character is an lowercase character
(function) [edit]
C++ documentation for islower
ASCII values characters

iscntrl
iswcntrl

isprint
iswprint

isspace
iswspace

isblank
iswblank

isgraph
iswgraph

ispunct
iswpunct

isalnum
iswalnum

isalpha
iswalpha

isupper
iswupper

islower
iswlower

isdigit
iswdigit

isxdigit
iswxdigit

decimal hexadecimal octal
0–8 \x0–\x8 0円–10円 control codes (NUL, etc.) ≠0 0 0 0 0 0 0 0 0 0 0 0
9 \x9 11円 tab (\t) ≠0 0 ≠0 ≠0 0 0 0 0 0 0 0 0
10–13 \xA–\xD 12円–15円 whitespaces (\n, \v, \f, \r) ≠0 0 ≠0 0 0 0 0 0 0 0 0 0
14–31 \xE–\x1F 16円–37円 control codes ≠0 0 0 0 0 0 0 0 0 0 0 0
32 \x20 40円 space 0 ≠0 ≠0 ≠0 0 0 0 0 0 0 0 0
33–47 \x21–\x2F 41円–57円 !"#$%&'()*+,-./ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
48–57 \x30–\x39 60円–71円 0123456789 0 ≠0 0 0 ≠0 0 ≠0 0 0 0 ≠0 ≠0
58–64 \x3A–\x40 72円–100円 :;<=>?@ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
65–70 \x41–\x46 101円–106円 ABCDEF 0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 ≠0
71–90 \x47–\x5A 107円–132円 GHIJKLMNOP
QRSTUVWXYZ 		0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 0
91–96 \x5B–\x60 133円–140円 [\]^_` 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
97–102 \x61–\x66 141円–146円 abcdef 0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 ≠0
103–122 \x67–\x7A 147円–172円 ghijklmnop
qrstuvwxyz 		0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 0
123–126 \x7B–\x7E 173円–176円 {|}~ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
127 \x7F 177円 backspace character (DEL) ≠0 0 0 0 0 0 0 0 0 0 0 0

AltStyle によって変換されたページ (->オリジナル) /