Starting other Shells in Unix

If you wish to run a new shell, type in the program that runs that shell at the command line.
The three primary UNIX shells are listed in the chart below along with the command that runs that shell.
Program Shell Comment/bin/sh Bourne A subset of Korn
/bin/ksh Korn A superset of Bourne
/bin/csh C Not compatible with Korn or Bourne

When you first login, you are interacting with your login shell. This shell is said to be running in the foreground since you can interact with it. When you run a new shell, your original shell is put into the background and your new shell is run in the foreground. Being in the background means that your shell is waiting, ready to run, in the memory of the computer, but that you cannot interact with it. When you exit the new shell, your original shell will be brought back into the foreground automatically and you can interact with it again.
The SlideShow below shows you how to start a new shell on the command line to run the ps command to look at which processes are running as you start new shells. The SlideShow will point out which shells are in the foreground and background as you go through these commands.

Click the exercise link below to practice running other shells from the command line.
Starting Shells - Exercise
The next lesson looks at the relationship between parent and child processes.