How to Compare Two Strings in C

Does nay one know how to Compare two Strings in C Programming? Say, my program is about to receive a string "DEF", and I want to test if the string really contains "DEF". What is the best way to test it?

Code:

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

int main()
{
  char w1[20];
  char wd2[20];

  printf("\n first character:\n1: ");
  scanf("%s", wd1);                             

  printf(" second character:\n 2: ");
  scanf("%s", wd2);                               

 
  if(strcmp(wd1,wd2) == 0)
    printf("identical words");
  else
    printf("%s comes before %s", (strcmp(wd1, wd2) > 0) ? wd2 : wd1, (strcmp(wd1, wd2) < 0) ? wd2 : wd1);
}

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With strncmp you only check the first someSaneCharLimit number of characters.strlen() returns the length of a string, excluding the null. If they are the same up to that point they will be equal i.e. strncmp("abcd", "abch", 3) would return a 0 whereas strncmp("abcd", "abch", 4) would return a number greater than 0.

Code:

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#include<stdio.h>
main()
{
 
     
  while(st1[i]!='/0' &&st2[i]!='/0')
      if(st1[i]!=st2[i])
          flag=1;
    if(flag==1)
  printf("equal");
}

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