function
<cctype>

tolower

int tolower ( int c );
Convert uppercase letter to lowercase
Converts c to its lowercase equivalent if c is an uppercase letter and has a lowercase equivalent. If no such conversion is possible, the value returned is c unchanged.

Notice that what is considered a letter may depend on the locale being used; In the default "C" locale, an uppercase letter is any of: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z, which translate respectively to: a b c d e f g h i j k l m n o p q r s t u v w x y z.

In other locales, if an uppercase character has more than one correspondent lowercase character, this function always returns the same character for the same value of c.

In C++, a locale-specific template version of this function (tolower) exists in header <locale>.

Parameters

c
Character to be converted, casted to an int, or EOF.

Return Value

The lowercase equivalent to c, if such value exists, or c (unchanged) otherwise.
The value is returned as an int value that can be implicitly casted to char.

Example

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/* tolower example */
#include <stdio.h>
#include <ctype.h>
int main ()
{
  int i=0;
  char str[]="Test String.\n";
  char c;
  while (str[i])
  {
    c=str[i];
    putchar (tolower(c));
    i++;
  }
  return 0;
}

Output:
test string.


See also