C++; Singleton Design Pattern

Singleton is a creational design pattern.
Provide one and only instance of an object.

#include using namespace std; 

class MySingleton 

{ 

      public: static MySingleton* iInstance; 

      public: static MySingleton* GetInstance(); 

      private: MySingleton(); 

}; 

MySingleton* MySingleton::iInstance = NULL; 

MySingleton::MySingleton() 

{ 

      cout << "Inside construtor ..." << endl; 

} 

MySingleton* MySingleton::GetInstance() 

{

      if ( iInstance == NULL ) 

      {  

           iInstance = new MySingleton(); 

      } 

     return iInstance; 

} 

void main() 

{ 

     MySingleton* obj; 

     obj = MySingleton::GetInstance(); 

}

Useful linux commands

Vi Editor:

    x          Delete character at cursor
    X          Delete character before cursor
    Y or yy  Yank (copy) current line into "unnamed" storage buffer.
    p          Paste unnamed storage buffer after current line.
    P          Paste unnamed storage buffer before current line.
    r           Replace character
    R          Overwrite characters from cursor onward
    s          Substitute one character under cursor continue to insert
    S          Substitute entire line and begin to insert at beginning of line
    J           Join current and following line into one line

• Use command: ":e filename"

       Start new edit session on specified file name without closing current vi /        vim editor process.

• Find/Replace:Example:

       :%s/fff/rrrrr/  -   For all lines in a file, find string "fff" and replace with                                   string "rrrrr" for the first instance on a line.

       :%s/fff/rrrrr/g -  For all lines in a file, find string "fff" and replace with                                   string "rrrrr" for each instance on a line.

       :%s/fff/rrrrr/gc - For all lines in a file, find string "fff" and replace with                                   string "rrrrr" for each instance on a line. Ask for                                           confirmation
       :%s/fff/rrrrr/gi - For all lines in a file, find string "fff" and replace with                                   string "rrrrr" for each instance on a line. Case                                               insensitive.

Extract or Unpack a tar File:

• To extract tar file of type:

       tar -xvf <filename>.tar

• To extract .tar.gz (gzip) file
  
  tar -xzvf <file name>.tar.gz
• To extract .tar.bz2 (bzip2) file

       tar -xjvf file.tar.bz2

• To extarct single file from tar file

        tar -xvf file.tar foo.txt 

        tar -xzvf file.tar.gz foo.txt 

        tar -xjvf file.tar.bz2 foo.txt

Where,
-x : Extract a tar ball.
-v : Verbose output or show progress while extracting files.
-f : Specify an archive or a tarball filename.
-j : Decompress and extract the contents of the compressed archive created by bzip2 program (tar.bz2 extension).
-z : Decompress and extract the contents of the compressed archive created by gzip program (tar.gz extension).