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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4.  
  5. // Concatenates string1 and string2.
  6. // Returns the concatenated (string1+string2), or NULL on errors.
  7. // NOTE: Memory for the returned string is allocated with malloc() 
  8. // by the function, so the caller is responsible to release it with
  9. // a call to free().
  10. char *StringConcat(const char *string1, const char *string2)
  11. {
  12.     char *stringResult;
  13.     size_t len1;
  14.     size_t len2;
  15.  
  16.     // Check for NULL pointers...
  17.     // (Return NULL, or whatever your design is...)
  18.     if (string1 == NULL || string2 == NULL) {
  19.         return NULL;
  20.     }
  21.  
  22.     len1 = strlen(string1);
  23.     len2 = strlen(string2);
  24.  
  25.     // +1 for terminating NUL ('\0')
  26.     stringResult = malloc(len1 + len2 + 1);
  27.     if (stringResult == NULL) {
  28.         return NULL; // Allocation error
  29.     }
  30.  
  31.     // Copy characters from first string    
  32.     // (exclduing the terminating NUL --> len1)
  33.     memcpy(stringResult, string1, len1);
  34.  
  35.     // Copy characters from second string
  36.     // (including the terminating NUL --> len2+1)
  37.     memcpy(stringResult + len1, string2, len2+1);
  38.  
  39.     // Return destination string pointer to the caller.
  40.     // NOTE: Memory must be freed by the caller calling free().
  41.     return stringResult;
  42. }
  43.  
  44.  
  45. // *** TEST ***
  46. int main(void)
  47. {
  48.     // Test the function
  49.     char * str = StringConcat("Hello ", "World");
  50.  
  51.     // Print the resulting string
  52.     printf("%s\n", str);
  53.  
  54.     // Don't forget to free() memory allocatd by the concat function
  55.     free(str);
  56.  
  57.     // All right
  58.     return 0;
  59. }
  60.  
Success #stdin #stdout 0s 2184KB
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Standard input is empty
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Hello World
https://ideone.com/TCNMQN
language:
C (gcc 8.3)
created:
10 years ago
visibility:
public

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