69

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

11 Answers 11

71

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

  1. ps -p$$ -ocmd=. (On Solaris, this may need to be fname instead of cmd. On OSX and on BSD should be command instead of cmd.)
  2. Check for $BASH_VERSION, $ZSH_VERSION, and other shell-specific variables.
  3. Check $SHELL; this is a last resort, as it specifies your default shell and not necessarily the current shell.
  • 4
    Should you mention $0 too? – Mikel Mar 18 '11 at 2:41
  • I don't like $0 because it's more complicated: (1) it may be just the basename, (2) it may have '-' on the front to designate it as a login shell. – geekosaur Mar 18 '11 at 2:44
  • ps -p$$ -ocmd="" is prettier :-) – asoundmove Mar 18 '11 at 3:51
  • 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 '12 at 21:49
  • 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. – Keith Thompson Mar 18 '14 at 1:51
41

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
  • 2
    Also does not work on fish. – Ron E Aug 7 '16 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 '16 at 23:00
8

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 
6

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.

  • 7
    ps | grep $$ can still give false positives if, for example, your current process is 1234 and there's a process 12345. – Keith Thompson Mar 18 '14 at 1:48
4

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.

3

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
  • this gives me my current directory name; also, under csh and tcsh it gives me Ambiguous output redirect. – iconoclast Aug 7 '15 at 0:17
2

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

echo $SHELL
  • 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 at 6:39
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.

  • 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. – Stéphane Chazelas Sep 7 '15 at 16:12
  • Yes, it now only selects the entries in /bin and /usr/bin – Stéphane Chazelas Sep 8 '15 at 9:57
  • @StéphaneChazelas Maybe it is better now? – user79743 Feb 25 '16 at 22:29
0

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" ] && shopt -q >/dev/null 2>&1; then                # bash
  MYSHELL=`command -v bash`
elif [ -x "$shell" ] && which setenv |grep builtin >/dev/null; then  # tcsh
  echo "DANGER: this script is likely not compatible with C shells!"
  sleep 5
  setenv MYSHELL "$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

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).

  • Steven D already mentioned it : ) – lese Dec 4 '15 at 9:08
-5

This works too:

env | grep SHELL

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