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

Question

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

Answer 1

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.

Answer 2

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

Answer 3

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 

Answer 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.

Answer 5

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.)

Answer 6

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

Answer 7

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.

Answer 8

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.

Answer 9

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.)

Answer 10

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).

Answer 11

This works too:

env | grep SHELL