The function definition of strcat() is:
char *strcat(char *destination, const char *source)
It is defined in the string.h header file.
strcat() arguments
As you can see, the strcat() function takes two arguments:
destination - destination string
	source - source string
The strcat() function concatenates the destination string and the source string, and the result is stored in the destination string.
Example: C strcat() function
#include <stdio.h>
#include <string.h>
int main() {
   char str1[100] = "This is ", str2[] = "programiz.com";
   // concatenates str1 and str2
   // the resultant string is stored in str1.
   strcat(str1, str2);
   puts(str1);
   puts(str2);
   return 0;
}
Output
This is programiz.com programiz.com
Note: When we use strcat(), the size of the destination string should be large enough to store the resultant string. If not, we will get the segmentation fault error.
