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Write C code to return a string from a function




This is one of the most popular interview questions

This C program wont work!


char *myfunction(int n)
{
   char buffer[20];
   sprintf(buffer, "%d", n);
   return retbuf; 
}



This wont work either!


char *myfunc1()
{
  char temp[] = "string";
  return temp;
}


char *myfunc2()
{
   char temp[] = {'s', 't', 'r', 'i', 'n', 'g', '\0'};
   return temp;
}


int main()
{
    puts(myfunc1());
    puts(myfunc2());
}




The returned pointer should be to a static buffer (like static char buffer[20];), or to a buffer passed in by the caller function, or to memory obtained using malloc(), but not to a local array.

This will work


char *myfunc()
{
   char *temp = "string";
   return temp;
}

int main()
{
   puts(someFun());
}


So will this


calling_function()
{ 
  char *string; 
  return_string(&string); 
  printf(?\n[%s]\n?, string);
}

boolean return_string(char **mode_string /*Pointer to a pointer! */) 
{ 
   *string = (char *) malloc(100 * sizeof(char)); 
   DISCARD strcpy((char *)*string, (char *)?Something?); 
}


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Last updated: November 3, 2005

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