strcmp misbehave with 2 same strings

Question

I have this code:

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

int main() {

  char s1[50], s2[50];

  printf("write s1:\n");
  fgets(s1, sizeof(s1), stdin);

  printf("s2:\n");
  fgets(s2, sizeof(s2), stdin);

  printf("The concatenation of the two strings: %s\n", strcat(s1, s2));

  if( strcmp(s2, s1) < 0 ) {
    printf("s2 is shorter than s1.\n");
  } else if( strcmp(s2, s1) > 0 ) {
    printf("s2 is longer than s1.\n");
  } else {
    printf("strings are equal.\n");
  }

  return 0;
}

The problem is that when I write 2 same strings like abc or whatever, strcmp return "s2 is shorter than s1."

Is that the normal output or have I done anything wrong? If so, where?

Or strcat makes the string not equal? Can anything be done about this?

Thank you

Answer 1

You are doing

 strcat(s1, s2)

before comparing. Which will modify string s1 so strings will not be equal

Answer 2

you are doing a strcat before doing doing strcmp. strcat would concatenate s2 to s1

Answer 3

Strcmp compares the strings according to the value of their contents (similar to the dictionary order, if you like, but not exactly that) not according to their length.

For example: "abc" > "abb"

Answer 4

Try replacing

    printf("The concatenation of the two strings: %s\n", strcat(s1, s2));

with

    printf("The two strings are: '%s' and '%s' and their concatenation: '%s'\n",
    s1, s2, strcat(s1, s2));

Then read a description of strcat .

If that doesn't help, replace %s sequences with %p . (Possibly you'll have to read a description of the %p format specifier in the printf documentation.)