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strlwr() function in C

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  • Difficulty Level : Medium
  • Last Updated : 04 Oct, 2018

The strlwr( ) function is a built-in function in C and is used to convert a given string into lowercase.


char *strlwr(char *str);


  • str: This represents the given string which we want to convert into lowercase.

Returns: It returns the modified string obtained after converting the characters of the given string str to lowercase.

Note: This is a non-standard function that works only with older versions of Microsoft C.

Below programs illustrate the strlwr() function in C:

Example 1:-

// C program to demonstrate
// example of strlwr() function
int main()
    char str[ ] = "GEEKSFORGEEKS IS THE BEST";
    // converting the given string into lowercase.
    printf("%s\n",strlwr (str));
    return  0;


geeksforgeeks is the best

Example 2:-

// C program to demonstrate
// example of strlwr() function.
#include <string.h>
int main()
  char str[] = "CompuTer ScienCe PoRTAl fOr geeKS";
  printf("Given string is: %s\n",str);
  printf("\nString after converting to the "
             "lowercase is: %s",strlwr(str));
  return 0;


Given string is: CompuTer ScienCe PoRTAl fOr geeKS

String after converting to the lowercase is: computer science portal for geeks

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