echo hello,world
echo $HOME

Frequently used Shell Variables:

• $USERNAME
• $HOME
• $HOSTNAME - Name of the machine where the shell is running.
• $PWD - Present Working directory
• $PATH

Special Shell Variables

• $0: Name of the shell.
• $$: Process ID of the shell.
• $?: Return exit code of previously run program.
• $-: flags set in the bash shell.

Process Control

• Use of & to run a job in the background.
• fg: Bring process to foreground.
• coproc :Running a command while also using the shell.
• jobs : List all the programs running un the background.
• top : Statistics of running processes.
• kill : Kill a process

Program Exit Codes