C Data Type Functions - C tolower

Converts a character to lowercase.

Prototype

int tolower( int ch );

Parameters

ch - character to be converted.

If the value of ch is not representable as unsigned char and does not equal EOF, the behavior is undefined.

Return value

Lowercase version of ch or unmodified ch if no lowercase version is listed in the current C locale.

Example


#include<stdio.h> 
#include<string.h> 
//  ww w .  j a  va2 s.  c  o m
int main(void) { 
  int loop; 
  char string[]="THIS IS A TEST"; 

  for(loop=0;loop<strlen(string);loop++) 
    string[loop]=tolower(string[loop]); 

  printf("%s\n",string); 
  return 0; 
}

The code above generates the following result.

Example 2


#include <stdio.h>
#include <ctype.h>
#include <locale.h>
#include <limits.h>
 /*w w  w.  j  av  a 2 s .  c om*/
int main(void)
{
    /* In the default locale: */
    unsigned char l;
    for (unsigned char u=0; u<UCHAR_MAX; u++) {
        l = tolower(u);
        if (l!=u) printf("%c%c ", u,l);
    }
    printf("\n\n");
 
    unsigned char c = '\xb4'; // the character ? in ISO-8859-15
                              // but ? (acute accent) in ISO-8859-1 
    unsigned char c2 = c;   // for printing
    setlocale(LC_ALL, "en_US.iso88591");
    printf("in iso8859-1, tolower('0x%x') gives 0x%x\n", c2, tolower(c));
    setlocale(LC_ALL, "en_US.iso885915");
    printf("in iso8859-15, tolower('0x%x') gives 0x%x\n", c2, tolower(c));
}

The code above generates the following result.