returns index of string s2 in string s1 and returns -1 if no substring s2 is found in s1. - C String

C examples for String:String Function

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Description

returns index of string s2 in string s1 and returns -1 if no substring s2 is found in s1. 

int strindex(char s1[], char s2[])
{
  int j, k, m;
  for(j = 0; s1[j] != '\0'; j++){
    for(k = j, m = 0; s2[m] != '\0' && s1[k] == s1[m]; k++, m++)
      ;                                              /* null statement */
    if(m > 0 && s2[m] == '\0')
      return j;
  }
  return -1;
}

Demo Code

#include <stdio.h>

int strindex(char s1[], char s2[])
{
  int j, k, m;//w  ww.j  a v  a2s. co  m
  for(j = 0; s1[j] != '\0'; j++){
    for(k = j, m = 0; s2[m] != '\0' && s1[k] == s1[m]; k++, m++)
      ;                                              /* null statement */
    if(m > 0 && s2[m] == '\0')
      return j;
  }
  return -1;
}



int main(void)
{
   char *str = "  this is a  test   ";
   
   char *s = "this";
   
   int index = strindex(str, s);

   printf("%d", index);

   return 0;
}

Result


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