Linux or Unix Viva questions

• What is the core of Linux Operating System?
• What is the basic difference between UNIX and Linux Operating System.
  
• Is Linux Operating system Virus free?
• Linux is which kind of Operating System?
• What is Shell's Responsibilities ?
• What is awk ?
• What is "grep" program ?
• What is Interactive mode Linux?
• What is environment variable?
• What is shell variable?
• Explain the “Exit” command?
• What is GUI Scripting?
• How can shell scripts be debugged in unix?
• What is use of sed command?
• What are links and symbolic links in UNIX file system?
• What are PIDs in linux?