Linux - Shell


Os - Shell in Linux context



The valid shell for a distribution are listed in the /etc/shells



Several type of unix_shell have been developed:


The following table shows the commonly used default UNIX® system prompt and superuser prompt for the C shell, Bourne shell, and Korn shell.

Shell Prompt
C shell machine_name%
C shell for superuser machine_name#
Bourne shell and Korn shell $
Bourne shell and Korn shell for superuser #

Current Shell

With the environment variable $SHELL

echo $SHELL

With ps

ps -p $$
  PID TTY          TIME CMD
 4104 pts/1    00:00:00 bash


  • $ is a bash special parameter that contains the PID (process identification number) of the current process which is your shell

Then running a ps on that number displays a process status listing of your shell.

Zero (0)

In bash, the special parameter 0 expands to the name of the shell or shell script. This is set at shell initialization. If bash is invoked with a file of com- mands, $0 is set to the name of that file.

If bash is started with the -c option, then $0 is set to the first argument after the string to be executed, if one is present. Otherwise, it is set to the file name used to invoke bash, as given by argument zero.

# echo $0

default shell for a user

The utility chsh (Change the login shell) is used to change it.

It will change it in the /etc/password file

absolute path name

See the special parameter $_

Documentation / Reference

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