String compare is not working as expected in c language

Question

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

int main() { 
  char str1[50]="TEST sun raised";
  char str2[4][90]={"sun","in"};
  char delim[] = " ";

  char *ptr=strtok(str1,delim);
  while (ptr!=NULL) {

    int i=0;
    for (i=0; i<4; i++) {
      if(strcmp(str2[i],ptr)) {
        printf("%s\n",ptr);
        break;
      }
      else {   
      }
    }

    ptr=strtok(NULL,delim);
  }

  return 0; 
}

Below code should return Test and raised but it returns all strings

Note: `strcmp(str2[i],ptr)` is true (non-0) when strings differ. Krishna Reddy CH, is this what you want? — chux - Reinstate Monica, Dec 01 '19 at 20:18
"Below code should return Test and raised but it returns all strings." I'm sorry but that statement doesn't make any sense. — robbpriestley, Dec 02 '19 at 01:21

phoenixstudio · Answer 1 · 2019-12-01T20:47:52.517

2

you need to adjust your test if(-1) C is true , and strcmp() does not return true or false , it return a number positive or negative , and zero if the two strings match, this means that if(strcmp(str2[i],ptr) is always true except when str2[i] matches ptr, you can resolve this by using somthing like this to find matches if(strcmp(str2[i],ptr) == 0) or if(!strcmp(str2[i],ptr)) which return true only if strcmp return 0 ,your test is equivalent to if(strcmp(str2[i],ptr) != 0) the reason why you can see sun in your results is : sun does not match with Test and raised , if you are trying to find strings that does not exist only, update your code to this

int main()
{
char str1[50]="TEST sun raised";
char str2[4][90]={"sun","in"};
char delim[] = " ";
 char *ptr=strtok(str1,delim);
 while(ptr!=NULL){
   int i=0;
   int found = 0;
   for( i=0;i<4;i++){
   if(strcmp(str2[i],ptr)==0){
         found++;
       break;
   }
}
if(found == 0) printf("%s does not exist \n",ptr);

ptr=strtok(NULL,delim);
}

edited Dec 01 '19 at 20:47

answered Dec 01 '19 at 20:18

phoenixstudio

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And the reason why the word "sun" appears to match, when `!=0` means it *wasn't* found, is because one of the *other* strings does not match. – Weather Vane Dec 01 '19 at 20:22
Consider what happens with `strcmp(str2[2],ptr)` – chux - Reinstate Monica Dec 01 '19 at 20:29
Change `if(strcmp(str2[i],ptr))` to `if(strcmp(str2[i],ptr) == 0)` after which your program outputs `sun`. – Weather Vane Dec 01 '19 at 20:29
are you trying to find matches or if it does not exist ? , the reason why you can see sun when you use `!=0` is because sun match wich sun but does not match with Test and raised => you will see it in the results – phoenixstudio Dec 01 '19 at 20:34
i want the string which doesnt exist in str2 array – Krishna Reddy CH Dec 01 '19 at 20:37

String compare is not working as expected in c language

1 Answers1