110

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

4
  • 4
    echo $SHELL, no? Aug 23, 2013 at 11:49
  • @innocent-world No, echo #SHELL is not quite it. See # 3 in the Answer by geekosaur. Feb 4, 2017 at 23:18
  • I am not so sure that "shell" has a well defined meaning. For example, you might run xterm -e /bin/cat but I am not happy calling /bin/cat a shell. Aug 24, 2017 at 10:26
  • Also some shells (like scsh) dont use POSIX shell like syntax. Aug 24, 2017 at 10:30

11 Answers 11

104

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$$ -ocommand=.)
  2. Check for $BASH_VERSION, $ZSH_VERSION, and other shell-specific variables.
  3. Check $SHELL; this is a last resort, as it specifies your default shell and not necessarily the current shell.
10
  • 6
    Should you mention $0 too?
    – Mikel
    Mar 18, 2011 at 2:41
  • I don't like $0 because it's more complicated: (1) it may be just the basename, (2) it may have '-' on the front to designate it as a login shell.
    – geekosaur
    Mar 18, 2011 at 2:44
  • 1
    @geekosaur: maybe so, but $0 still seems more useful than $SHELL: wouldn't you agree? You could always pipe it through sed to remove the '-'.
    – iconoclast
    Aug 29, 2012 at 21:49
  • 5
    On Mac, #1 is ps -p $$ -o comm="". Also, for those wondering, $$ is the shell process ID.
    – duozmo
    Oct 19, 2013 at 18:00
  • 2
    If you're running tcsh, $tcsh and $version will be set. These are shell variables, not environment variables. If you're running a non-tcsh version of csh, I don't think there are any distinctive variables. And of course the syntax used to check variables differs between csh/tcsh on the one hand, and sh/ksh/bash/zsh on the other. Mar 18, 2014 at 1:51
58

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

$ ps -p $$

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

$ echo $0
3
  • 2
    Also does not work on fish.
    – Ron E
    Aug 7, 2016 at 15:27
  • I think that @jiliagre's answer is probably would I would use today. On fish %self can be used in place of $$
    – Steven D
    Aug 27, 2016 at 23:00
  • 1
    It would be great if you explained what you are doing, why this works, what the $$ is etc Aug 5, 2020 at 18:00
9

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:

$ ps -o comm= -p $$
ksh93 
8

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.)

1
  • 9
    ps | grep $$ can still give false positives if, for example, your current process is 1234 and there's a process 12345. Mar 18, 2014 at 1:48
7

There are two really simple ways:

  • Using ps command:

    ps -o comm= $$
    

    or

    ps -h -o comm -p $$
    

    where:

    • -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 <PID> list only process whith PID form list suplied.
  • Using the /proc process information pseudo-file system:

    cat /proc/$$/comm
    

    This option behaves exactly as the ps command above.

    or

    readlink /proc/$$/exe
    

    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

    basename $(readlink /proc/$$/exe)
    

    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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  • 2
    basename $(readlink /proc/$$/exe) is Korn/POSIX shell syntax. Won't work in csh/tcsh/rc/es/akanga/fish. $$ won't work in rc/es/akanga/fish. Oct 9, 2020 at 7:27
  • basename $(readlink /proc/$$/exe) is the only command here that could work for me in a docker image with no ps installed.
    – Flavin
    Apr 21, 2021 at 13:15
4

A mix of all the other answers, compatible with Mac (comm), Solaris (fname) and Linux (cmd):

ps -p$$ -o cmd="",comm="",fname="" 2>/dev/null | sed 's/^-//' | grep -oE '\w+' | head -n1
2
  • this gives me my current directory name; also, under csh and tcsh it gives me Ambiguous output redirect.
    – iconoclast
    Aug 7, 2015 at 0:17
  • This is also what Anaconda uses (version 2022.05) in it's [env]/bin/activate script to detect shell type. A comment in that file explicitly links to this answer.
    – Neinstein
    Jun 10 at 11:41
3

If you have it saved in your environment variables you can use the following:

echo $SHELL

For accuracy in many different shells you should use

ps -p $$

Why does this work?

echo $$ # 998

What is that number?

It's the process id of the current shell.

$ expands to the same value as the current shell.

$$ process ID of the parent in a sub shell

If you only want then name of the shell you could use

ps -p $$ | awk '{if(NR>1)print}' | awk '$0=$NF' | tr -d -

In a nutshell we are taking the output of the process sub shell and piping it to some formatting tools awk, sed and tr all work for this, removing the first 3 columns, the first line of output, and then the - gives just the name of the shell. Consider putting that into a function for ease later.

2
  • That will most likely return the pathname of the shell executable of your login shell. It is not certain that the login shell is what you are currently running though.
    – Kusalananda
    Apr 10, 2019 at 6:39
  • I have updated my answer to provide more value and understanding. Aug 5, 2020 at 18:16
2

I set $MYSHELL for future tests in my shell-agnostic ~/.aliases:

unset MYSHELL
if [ -n "$ZSH_VERSION" ] && type zstyle >/dev/null 2>&1; then           # zsh
  MYSHELL=`command -v zsh`
elif [ -x "$BASH_VERSION" ] && type caller >/dev/null 2>&1; then        # bash
  MYSHELL=`command -v bash`
elif [ -x "$shell" ] && which setenv |grep -l builtin >/dev/null; then  # tcsh
  echo "DANGER: this script is likely not compatible with C shells!"
  sleep 5
  setenv MYSHELL "$shell"
fi

# verify
if [ ! -x "$MYSHELL" ]; then
  MYSHELL=`command -v "$(ps $$ |awk 'NR == 2 { print $NF }')"`
  [ -x "$MYSHELL" ] || MYSHELL="${SHELL:-/bin/sh}"  # default if verify fails
fi

The tcsh section is likely unwise to roll into a POSIX-style script since it's so radically different (thus the warning and five second pause). (For one, csh-style shells can't do 2>/dev/null or >&2, as noted in the famous Csh Programming Considered Harmful rant.)

1

The pid of the running shell is given by the var $$ (in most shells).

whichsh="`ps -o pid,args| awk '$1=='"$$"'{print $2}'`"
echo "$whichsh"

Using backticks to make jsh (Heirlomm shell) work.

In many shells the direct test of ps -o args= -p $$ works, but busybox ash fails on that (solved).

The check that $1 must be equal to $$ removes most false positives.

The last ;: are used to keep the shell running for ksh and zsh.

Tests on more systems will help, please make a comment if it doesn't work for you.

Does not work in csh type of shells.

3
  • On OS/X, in my tests, I get at least 3 lines, one for the shell, one for /usr/lib/dyld, one for /private/var/db/dyld/dyld_shared_cache_x86_64. Sep 7, 2015 at 16:12
  • Yes, it now only selects the entries in /bin and /usr/bin Sep 8, 2015 at 9:57
  • @StéphaneChazelas Maybe it is better now?
    – user79743
    Feb 25, 2016 at 22:29
-1

You can simply use echo $0 command to check which shell you are using and <name_of_the_shell> --version to check the version of the shell. (eg. bash --version).

1
  • Steven D already mentioned it : )
    – lese
    Dec 4, 2015 at 9:08
-6

This works too:

env | grep SHELL
1

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