...
The getline() function is similar to the fgets() function but can dynamically allocates allocate memory for the input buffer. If passed a null pointer, getline() dynamically allocates a buffer of sufficient size to hold the input. If instead, you pass a pointer to dynamically allocated storage that is too small to hold the contents of the string, the getline() function resizes the buffer, using realloc(), rather than truncating the input. If successful, the getline() function returns the number of characters read, which can be used to determine if the input has any null characters before the newline. The getline() function works only with dynamically allocated buffers. Allocated memory must be explicitly deallocated by the caller to avoid memory leaks (see MEM31-C. Free dynamically allocated memory when no longer needed.)
...