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Saturday, January 16, 2021

How to Check Which Shell You are Using on Linux

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Out of the box, Linux provides a wide variety of shells. There’s bash (Bourne Again shell) shell which ships by default in many systems. We also have sh (Bourne Shell), tcsh (TC shell), csh (C shell), Zsh (Z shell) and ksh (Korn  Shell). Curious to know which shell you are using on your Linux system? In this guide, we explore different ways that you can use to check which shell you are using in Linux.

1) Using echo command

The Linux echo command is a built-in command that is used to print the output of a string which is passed as an argument. Additionally, you can use the echo command to check the shell that you are running commands in. To accomplish this, execute:

$ echo $SHELL

which shell you are using in Linux

The output shows that I am using the bash shell. Additionally, you can simply run the command:

$ echo $0

print which shell you are in

 

To get the PID of the  shell that you are currently in, run:

$ echo $$

print shell variable

2) Using ps command

Commonly used for listing running processes, the ps command in its basic format sheds light on the shell that you are using.  Simply execute the command:

$ ps

check shell using ps command

From the first line of the output, we can clearly see the PID of the shell and the last column prints out the type of shell, in this case – bash.

Alternatively, you can run the command:

$ ps -p $$

check which shell you are using using ps command

 

3) Check shell  by viewing the /etc/passwd file

The grep command can be used to probe the /etc/passwd file that contains attributes of the users such as username, user ID and group ID.

To display the shell used, invoke the command:

$ grep "^$USER" /etc/passwd

grep command to find the bash used

At the very last segment, we get to see the bash used, in this case /bin/bash This also gives you a glimpse of which shell is opened first when you first log in to your system.

3) Check shell using the lsof command

Ordinarily, the lsof command, short for list of open files,  is used to provide a list of open files on your system. However, when used with the -p $$ flag, it gives a pointer to the shell you are in when you look at the first column of the output.

For example, we can clearly see that we are on the bash shell.

$ lsof -p $$

lsof -p command

How to check the valid login shells

We have seen various ways that you can employ to check the shell that you are currently in. If you want to know the valid shells on your system, check the /etc/shells file, This file will provide you with the full pathnames of valid login shells in your system. Using the cat command, view the file as shown:

$ cat /etc/shells

Check-valid-login-shells

Conclusion

In this guide, we have shared simple but nifty ways that you can use to know which shell you are working on. This is important when writing scripts so that you can know how to start off writing the shebang header. We do hope that this tutorial was beneficial. Send us a shout and don’t forget to share this guide on your social platforms.

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