Use the function toupper() in combination with the .strstr() function to find out whether one string occurs in another, ignoring case. - C String

Description

Use the function toupper() in combination with the .strstr() function to find out whether one string occurs in another, ignoring case.

Demo Code

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define TEXT_LEN 100                   // Maximum input text length
#define SUBSTR_LEN 40                  // Maximum substring length

int main(void)
{
  char text[TEXT_LEN];                 // Input buffer for string to be searched
  char substring[SUBSTR_LEN];          // Input buffer for string sought

  printf("Enter the string to be searched (less than %d characters):\n", TEXT_LEN);
  gets_s(text, TEXT_LEN);//from  w ww.ja  v a 2s.  com

  printf("\nEnter the string sought (less than %d characters):\n", SUBSTR_LEN);
  gets_s(substring, SUBSTR_LEN);

  printf("\nFirst string entered:\n%s\n", text);
  printf("Second string entered:\n%s\n", substring);

  // Convert both strings to uppercase.
  for(int i = 0 ; (text[i] = (char)toupper(text[i])) != '\0' ; ++i);
  for(int i = 0 ; (substring[i] = (char)toupper(substring[i])) != '\0' ; ++i);

  printf("The second string %s found in the first.\n",
              ((strstr(text, substring) == NULL) ? "was not" : "was"));
  return 0;
}

Result

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