strlwr() to change string from uppercase to lowercase chars in C program

#include <stdio.h>
#include <string.h>
int main(void){
   char str[]="PLUS2NET";
   printf("%s\n",strlwr (str));
   return 0;
}

The output of above code is here

plus2net

We can change uppercase letters to lowercase letters by using strlwr() string function.

strlwr(input_string);

The strlwr() function is not part of the C standard library, meaning some compilers may not support it. For cross-platform compatibility, it's advisable to write your own implementation for converting strings to lowercase. This ensures your code functions reliably across different systems and compilers.

char *strlwr(char *str)
{
  unsigned char *p = (unsigned char *)str;

  while (*p) {
     *p = tolower((unsigned char)*p);
      p++;
  }

  return str;
}

Example : using strlwr() with user input string

#include <stdio.h>
#include <string.h>
char *strlwr(char *str)
{
  unsigned char *p = (unsigned char *)str;

  while (*p) {
     *p = tolower((unsigned char)*p);
      p++;
  }

  return str;
}
int main(void){
   char str[100];
   printf("Enter any string");
   scanf("%s",str);
   printf("Output: %s",strlwr(str));
   return 0;
}

Output

PLUS2NET
plus2net

Example: Converting Array of Strings

#include <stdio.h>
#include <string.h>

char *strlwr(char *str) {
    unsigned char *p = (unsigned char *)str;

    while (*p) {
        *p = tolower((unsigned char)*p);  // Use tolower to convert characters
        p++;
    }

    return str;
}

int main() {
    char strings[3][20] = {"HELLO", "WORLD", "PLUS2NET"};
    for (int i = 0; i < 3; i++) {
        printf("Lowercase: %s\n", strlwr(strings[i]));
    }
    return 0;
}

Output

Lowercase: hello
Lowercase: world
Lowercase: plus2net

String Functions Scripts strupr() C- Tutorials

strlwr(): Uppercase to Lowercase

Example : using strlwr() with user input string

Example: Converting Array of Strings

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