copy [C++ Reference]
Keywords: string,copy
Date: 2009-10-10T19:38:22-0700

[[copy]]
C++ Reference
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## copy

Syntax:

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

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.

Related Topics: substr

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