tolower
Header: <ctype.h>
Converts the given character to lowercase according to the character conversion rules defined by the currently installed C locale.
# Declarations
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 <ctype.h>
#include <locale.h>
#include <limits.h>
int main(void)
{
/* In the default locale: */
for (unsigned char u = 0; u < UCHAR_MAX; u++) {
unsigned char l = tolower(u);
if (l != u) printf("%c%c ", u, l);
}
printf("\n\n");
unsigned char c = '\xb4'; // the character Ž in ISO-8859-15
// but ´ (acute accent) in ISO-8859-1
setlocale(LC_ALL, "en_US.iso88591");
printf("in iso8859-1, tolower('0x%x') gives 0x%x\n", c, tolower(c));
setlocale(LC_ALL, "en_US.iso885915");
printf("in iso8859-15, tolower('0x%x') gives 0x%x\n", c, tolower(c));
}