string:copy

C++ Reference

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copy

Syntax:

    #include <string>
    size_type copy( char* str, size_type num, size_type index = 0 );

The copy() function copies num characters of the current string (starting at index if it's specified, 0 otherwise) into str. The return value of copy() is the number of characters copied. For example, the following code uses copy() to extract a substring of a string into an array of characters:

   char buf[30];
   memset( buf, '\0', 30 );
   string str = "Trying is the first step towards success.";
   str.copy( buf, 24 );
   cout << buf << endl;

When run, this code displays:

   Trying is the first step

Note that before calling copy(), we first call (Standard C String and Character) memset() to fill the destination array with copies of the NULL character. This step is included to make sure that the resulting array of characters is NULL-terminated.