• Both Linux and Unix come with a variety of shells pre-installed. By default, bash (Bourne Again shell), ksh (Korn shell), csh/tcsh (TC shell), sh (Bourne shell), and other shells are installed.
• It should work with the echo or printf commands below:
• echo '$SHELL'
• Please note that $SHELL is the current user's shell, not necessarily the shell that is now running.
  
• Here's another useful Unix tip. Use the ps command with the -p pid parameter. The command below picks all processes with process ID numbers in pid. To figure out which shell you're in, run the following command:
• ps -p $$

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