Sfdwhf

The short version (thx @Serg)

cat /etc/alternatives/x-terminal-emulator

The long version

sudo update-alternatives --config x-terminal-emulator

and look for the * in the output

;)

Example output

There are 7 alternatives which provide `x-terminal-emulator’.

Selection Alternative

———————————————–

    1 /usr/bin/xterm

    2 /usr/bin/uxterm

    3 /usr/bin/koi8rxterm

    4 /usr/bin/lxterm

 *+ 5 /usr/bin/gnome-terminal.wrapper

    6 /usr/bin/konsole

    7 /usr/bin/xfce4-terminal.wrapper

Press enter to keep the default[*], or type selection number:

Or, thanks to @muru, here is more detailed output

$ update-alternatives --display x-terminal-emulator

x-terminal-emulator - auto mode

  link currently points to /usr/bin/gnome-terminal.wrapper

/usr/bin/gnome-terminal.wrapper - priority 40

  slave x-terminal-emulator.1.gz: /usr/share/man/man1/gnome-terminal.1.gz

/usr/bin/koi8rxterm - priority 20

  slave x-terminal-emulator.1.gz: /usr/share/man/man1/koi8rxterm.1.gz

/usr/bin/lxterm - priority 30

  slave x-terminal-emulator.1.gz: /usr/share/man/man1/lxterm.1.gz

/usr/bin/mate-terminal.wrapper - priority 30

  slave x-terminal-emulator.1.gz: /usr/share/man/man1/mate-terminal.1.gz

/usr/bin/uxterm - priority 20

  slave x-terminal-emulator.1.gz: /usr/share/man/man1/uxterm.1.gz

/usr/bin/xterm - priority 20

  slave x-terminal-emulator.1.gz: /usr/share/man/man1/xterm.1.gz

Current 'best' version is '/usr/bin/gnome-terminal.wrapper'.

Shell vs Terminal

First thing we need to have clarified is what exactly is being asked - find out the running shell or running terminal. Often these two terms are used interchangeably, but they are different things altogether. Shell is the command-line interpreter, specifically interactive shell is the prompt plus text field where you enter commands. Shells can also be non-interactive, for example a script starts non-interactive shell, or bash -c 'echo hello world' also starts non-interactive shell.

By contrast, terminal is the interface to shell ( though it could be another application as well). Originally terminal referred to actual hardware, but nowadays they're mostly software. What you see when you press Ctrl+Alt+t or click on the terminal icon in GUI, that starts a terminal emulator, a window which mimics behavior of hardware, and within that window you can see the shell running. Ctrl+Alt+F2 (or any of the 6 function keys) will open virtual console, aka tty. I recommend reading Why is a virtual terminal “virtual”, and what/why/where is the “real” terminal? for more info on the specifics.

Getting the shell information

Each user has a default shell assigned to them in /etc/passwd for their username. Assuming you are using default configuration and haven't called another shell explicitly as a command, it is sufficient to do:

echo $SHELL

But of course this only shows default value. Suppose we do the following:

user@ubuntu:~$ dash

$

We were originally in bash, but started interactive session of /bin/dash, Ubuntu's POSIX or system shell. The variable $SHELL won't change, because that's not its purpose - it shows default not current value. We will need to approach this from another perspective - the perspective of a process, which is something I've covered in Am I using bash or sh?

$ echo $$

4824

$ cat /proc/4824/comm                                                          

mksh

$ bash

xieerqi@eagle:~$ echo $$

6197

xieerqi@eagle:~$ cat /proc/6197/comm

bash

Here we take advantage of /proc/ filesystem. The name of the process and command-line parameters are displayed in /proc/<pid>/comm. All we need is to provide shell's PID, which is what $$ does. In the example above I am adding that separately, but there is nothing stopping us from doing just

cat /proc/$$/comm

Another way we could approach this is via checking where /proc/<pid>/exe. This file is a symlink that points to the executable file.

You can also do ps aux | grep $(echo $$ ) for that same purpose.

If you want to know filename or device name which is connected to stdin. (mostly useful in tty), run tty command

Many terminals seem to mask themselves as xterm compatible, which is reported by echo $TERM or echo $COLORTERM. Virtual terminals are more tricky, as you can see.

What we can do is run xprop, click on the desired window, grep its pid, and find out what's the name of that process matching pid. Or in other words:

$ ps aux | grep $(xprop | awk -F'='  '/PID/ {print $2}')                       

xieerqi   2124  0.6  1.7 208068 34604 ?        Sl   18:47   1:49 gnome-terminal

Or even more simply :

ps -p $(xprop | awk -F'=' '/PID/ {print $2}')

If you want to know the terminal program you are using, use this:

ps -o 'cmd=' -p $(ps -o 'ppid=' -p $$)

Run this just after opening the terminal (shell) without forking any further shell instance.

When you open up the terminal program, it basically spawns a child program, a shell. So the parent of the spawned shell is the terminal itself. In other words, the PPID of the shell is the PID of terminal program.

Here we are finding the parent process ID (PPID) of the shell (bash) by ps -o 'ppid=' -p $$ , which will be the process ID of terminal program.

Then we are finding the process name from the PID:

$ ps -o 'cmd=' -p $(ps -o 'ppid=' -p $$)

gnome-terminal

It is basically a one liner of:

$ ps -o 'ppid=' -p $$

 2268



$ ps -o 'cmd=' -p 2268

gnome-terminal

Type in printenv from the terminal window to view all variables of the open session.

Type in echo $COLORTERM from the terminal window. NOTE: this does not work with all terminals, one like sakura does not report this back.

root@terrance-Linux:~# echo $COLORTERM

gnome-terminal

the one below is from an aterm terminal.

root@terrance-Linux:~$ echo $COLORTERM

rxvt-xpm

If you just want the name of the terminal program, you'll most probably find it under Help > About.

cat /etc/alternatives/x-terminal-emulator | grep exec

Sample output:

exec('gnome-terminal',@args);

There's the answer for my system: gnome-terminal.

So, typing gnome-terminal into my terminal will now open up another identical terminal window.

Sources:

• Sergiy Kolodyazhnyy's comment under A.B.'s answer.

Simple answer. Works for both console or ssh.

Example for simple character terminal:

ssh username@systemname

echo $TERM

dumb

tells you that you can't open GUI apps on that connection

Example for xterm (also works with PuTTY/Xming on Windows)

ssh -Y username@systemname      -- omit this if using PuTTY --

echo $TERM

xterm

means that you can use GUI commands like opening the leafpad editor or nautilus file manager.

On the console it is the same:

Open terminal window

echo $TERM

xterm