Constructing Public or Private Keys

All System V IPC objects can be constructed using a public key. There are two ways to construct either type of key in an object-oriented way.

Constructor

os_key( key_t value )

Constructs the object with value value .

 

Constructor

os_key( const string& filename , char project_code )

Constructs the object using filename and project_code as a seed. The filename variable must exist in the file system.

The second approach to allocating keys is useful when two or more projects are using System V IPC. As long as each project has a unique filename, the project allocates different keys. The two techniques for allocating keys are illustrated in the following example.

#include <iostream>
#include <ospace/unix.h>

// Name of project directory.
string project = "/usr/tmp";

int
main()
  {
  os_unix_toolkit initialize;

  // Create key with specified id.
  os_key key1( 10 );
  cout << "key1 = " << key1 << endl;

  // Create key using filename "/usr/tmp" and project code 1.
  os_key key2( project, 1 );
  cout << "key2 = " << key2 << endl;

  // Create key using filename "/usr/tmp" and project code 2.
  os_key key3( project, 2 );
  cout << "key3 = " << key3 << endl;
  return 0;
  }

key1 = os_key( 10 )
key2 = os_key( 25575969 )
key3 = os_key( 42353185 )

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