Linux check what shell

Different Ways to Check Which Shell You are Using on Linux

A shell is a program through which users can interact with the Operating System. Linux provides commonly 4 types of Shell The Bourne Shell ( /bin/sh or /sbin/sh ), The C shell ( /bin/csh ), The Korn Shell ( /bin/ksh ), The GNU Bourne-Again Shell ( /bin/bash ). This article is about to Check that which shell we are using. Here, we discuss five ways by which we can check which shell we are using.

1) Using echo command: Basically, the echo command is used to print the input string, but it is also used to print the name of the shell which we are using with the help of the command.

2) Using ps command: ps command stands for “Process Status”. It is used to check the currently running status and their PIDs. If the ps command is run generally in the shell then it simply tells the name of the shell.

2. Shell name using ps

The first column tells the PID and the last column tells the type of shell i.e. bash.

3) By viewing /etc/passwd file: This tells the feature of the user just like it’s name, shell, and ID. This command is used with the grep command.

4) Using lsof command: lsof stands for LIST OF OPEN FILES. This command used when we want the list of open files in our system. By using the specific flag it gives a pointer to the shell and tells us about that which shell are we using and that specific flag is -p $$. The command looks like.

As you can see clearly in the 3rd line it tells us about the shell we are using.

5) Using readlink /proc/$$/exe: The readlink is used to print the file name. So with the help of this, we print the location of the current shell using the /proc/$$/exe. Command can be written as

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How do I find out what shell I am using on Linux/Unix?

B oth Linux and Unix provides various shell out of the box. One can find bash (Bourne Again shell), ksh (Korn shell), csh (C shell)/tcsh (TC shell), sh (Bourne shell) and more installed by default. However, how do you check which shell am I using? What is the best way to find out what shell I am using on Linux? The echo $SHELL is not so reliable. This page explains how to find out which shell I am using at a Linux, MacOS, FreeBSD, or Unix-like systems.

How can I find out what shell I am using?

The following echo command or printf command should work:
echo «$SHELL»
OR
printf «My current shell — %s\n» «$SHELL»
Please note that $SHELL is the shell for the current user but not necessarily the shell that is running at the moment. Try the following examples

How do I check which shell am I using?

Here is another old good Unix trick. Use the ps command with -p option. The following command selects the processes whose process ID numbers appear in pid. Use the following command to find out which shell you are in:
ps -p $$
Sample outputs:

So what is a $ argument passed to the -p option? Remember $ returns the PID (process identification number) of the current process, and the current process is your shell. So running a ps on that number displays a process status listing of your shell. In that listing, you will find the name of your shell (look for CMD column).
ps -p $$
Sample outputs:

From my Linux box:
ps -p $$
Sample outputs:

You can store your shell name in a variable as follows :
MYSHELL=`ps -hp $$|awk ‘‘`
Please note those are backquotes, not apostrophes. Or better try out the following if you have a bash shell:
MYSHELL=$(ps -hp $$|awk ‘‘)
Another option is as follows:
echo $0
OR
printf «%s\n» $0
Sample outputs from the above commands:

Fig.01: Linux check which shell am I using

How do I check how many shells are installed on my Linux box?

The /etc/shells is a text file which contains the full pathnames of valid login shells. Type the following [nixmd name=”cat”] to see list how many shells are installed on your Linux or Unix box:
cat /etc/shells

Use /etc/shells file to check how many shells are installed on your system

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Okay, so when I open the Terminal app, which shell is opened by default?

Your default shell is defined in /etc/passwd file. So try the following grep command:

How to check which shell am I using:

Use the following Linux or Unix commands:

1. ps -p $$ – Display your current shell name reliably.
2. echo «$SHELL» – Print the shell for the current user but not necessarily the shell that is running at the movement.
3. echo $0 – Another reliable and simple method to get the current shell interpreter name on Linux or Unix-like systems.
4. readlink /proc/$$/exe – Another option to get the current shell name reliably on Linux operating systems.
5. cat /etc/shells – List pathnames of valid login shells currently installed
6. grep «^$USER» /etc/passwd – Print the default shell name. The default shell runs when you open a terminal window.
7. chsh -s /bin/ksh – Change the shell used from /bin/bash (default) to /bin/ksh for your account

Conclusion

Sometimes things are not easy as they seem, and this page is the perfect example of it. I hope you found the suggestion useful when it comes to checking your current running shell. Bash users can display shell version by typing the following command:
$ bash —version
Here is what I got from my Ubuntu Linux 20.04 LTS desktop:

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How to Change Shell in Linux

This quick tutorial shows how to check the running shell, available shell in the system and how to change the default shell in Linux.

You probably are already aware that there are several shell available on Linux and other Unix-like systems. Bash is the default shell on almost all the Linux distributions but there are some other popular shells available such as:

Some of the shells provide additional features in a more user-friendly way. Take Fish shell for example. It partially starts showing you command hints based on your previous typed command. It’s quite handy if you don’t want remember the Linux terminal shortcuts all the time.

Let’s see a few things around shell in your Linux system.

How to know the default shell?

To know the default shell set for you in your Linux system, you can check the SHELL environment variable. Usually, the default shell is bash and it is shown like this:

How to see what shell are you currently using?

There is no single method that will tell you which shell you are using with 100% accuracy.

You can try either echo $0 that shows you an output like this:

or check the process using ps -p $$ like this:

How to see all the shells available on your Linux system?

All the shells available on your Linux systems are listed in the file /etc/shells. You can use cat command or less command to view the content of the file.

How to change the shell to use another one?

If you want to use a different shell, you can simply type its name and you’ll be logged into the new shell. For example, if you install zsh and want to use it, you can simply use:

You can enter exit to exit from the new shell and return to the previous one.

How to change the default shell in Linux permanently?

Suppose you liked the Fish shell a lot and you want to use it as your default shell so that every time you open the terminal or ssh into the system, you are using it instead of the default bash shell.

Linux allows you to change the default shell using the chsh command. The best way to change the default shell for your own logged in user is by specifying the shell name listed in the /etc/shells file with the -s option.

You must log out of the system so that the changes take into effect otherwise you’ll think that running chsh didn’t change the shell.

Did you notice that I had to specify the full path as it was listed in the /etc/shells file? If I had used chsh -s fish, it would have given me an error like “chsh: fish is an invalid shell”.

Which shell do you like?

Now that you know how to change shell, you may also read how to change users in Linux.

I hope this little article helped you to change the shell in Linux. If you have thought about changing the default shell, perhaps you use something other than the bash shell. Which shell is it? Why do you prefer it over the others?

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How to test what shell I am using in a terminal?

How to check what shell I am using in a terminal? What is the shell I am using in MacOS?

11 Answers 11

Several ways, from most to least reliable (and most-to-least «heavy»):

1. ps -p$$ -ocmd= . (On Solaris, this may need to be ps -p$$ -ofname= and on macOS and on BSD should be ps -p$$ -ocommand= .)
2. Check for $BASH_VERSION , $ZSH_VERSION , and other shell-specific variables.
3. Check $SHELL ; this is a last resort, as it specifies your default shell and not necessarily the current shell.

I’ve found that the following works in the four shells I have installed on my system (bash, dash, zsh, csh):

The following works on zsh, bash, and dash, but not on csh:

As the question asks for the shell used and does not talk about the potential arguments passed to it, here is a way that avoid showing them:

A note about some lighter implementations (Android phones, busybox, etc.): ps doesn’t always have support for the -p switch, but you can accomplish the search with a command like ps | grep «^$$ » . (This grep regex will uniquely identify the PID, so there will not be any false positives.)

There are two really simple ways:

• -h or finishing all options with = for not showing any header.
• -o comm for showing only the process basename ( bash instead of /bin/bash ).
• -p

list only process whith PID form list suplied.

Using the /proc process information pseudo-file system:

This option behaves exactly as the ps command above.

This /proc/PID/exe links to the file being executed, which in this case would point to /bin/bash, /bin/ksh, etc.

For getting only the name of the shell you can just use

This is the only option that will always give the same result even if you are in an script, sourced code, or terminal, as links to the binary of the shell interpreter in use.

Warning You must be aware that this will show the ultimate binary, so ksh may be linked to ksh93 or sh to bash.

The usage of /proc is really useful via the /proc/self , which links to the PID of the current command.

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How do I check which shell I am using?

I read that terminal is nothing but shell, and Unix provides different flavors of shells:

• Bourne shell (sh)
• C shell (csh)
• TC shell (tcsh)
• Korn shell (ksh)
• Bourne Again shell (bash)

Questions:

• When I open a terminal window, which shell is opened by default?
• How do I check how many shells are installed?
• How do I change the shell used from my account?

9 Answers 9

You can type the following command in your terminal to see which shell you are using:

The result will look something similar to the below if you are using the bash (Bourne Again Shell) terminal:

To find the shell you have on the default environment you can check the value of the SHELL environment variable:

To find the current shell instance, look for the process (shell) having the PID of the current shell instance.

To find the PID of the current instance of shell:

Now to find the process having the PID:

Putting it together:

$SHELL gives you the default shell. $0 gives you the current shell.

For example: I have bash as my default shell, which I use for my Terminal App. But for my iTerm2 app, I use the command as the window opens: /bin/ksh .

So my $0 gives me /bin/ksh on iTerm2. $SHELL gives me /bin/bash on iTerm2. $0 , $SHELL gives me /bin/bash on Terminal

The other answers tend to be using shell specific features, but we are trying to discover which shell we are using, so they assume the answer to the problem. For example none of the answers will work on fish.

Instead use the $$ syntax in an invocation of sh, but then we are looking for the PPID not the PID. Use the PPID to find the cmd.

Thanks for improvement @muru

To know which is the default shell for your user, you can run:

For example if you’re using Bash you should get the following output:

If you didn’t change any configuration it should be Bash since Bash it’s the default shell on Ubuntu.

The original post asked three questions. The answers given do cover the first question, «When I open a terminal window, which shell is opened by default?» They also answer a question which was NOT asked, namely «How can I find out which shell is currently running in the terminal?» However, as far as I can see nobody has answered either the second or third questions originally asked, namely «How do I check how many shells are installed?» and «How do I change the shell used from my account?»

To answer «How do I check how many shells are installed?» the following command will list all the available shells:

For example, on a default installation of Ubuntu 18.10 this gives:

However, by default sh is a symbolic link to dash, while rbash links to bash with the option -r («restricted bash») so there are actually only two shells, not four as the above list suggests. The following command will show you whether any of the listed shells are in fact symbolic links, and if so where they link to: ls -l /bin

Now for the question «How do I change the shell used from my account?» Assuming this means «How do I permanently change the default shell that a terminal will use», there is an answer here.

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