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

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 5

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 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

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 9

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 10

Good question me too on my Mac had the same doubt.

Another method, dirty but "it works", it really simple; you should launch a command that does not exist. The the shell reply the classical "command not found", but first shows its name. :-)

~$ piripicchio
-bash: piripicchio: command not found

and

~ % piripicchio
zsh: command not found: piripicchio`

---

Also, you could note that zsh prompt is "%" and bash is "$" but my root on bash has "%" too.

Answer 11

For anyone wanting to check the current shell in a shell script using a shebang (because the other answers will give the script name in this case):

ps -p$PPID

or to get only the name:

ps -p$PPID | grep -v "PID" | awk '{print $4}'

Explanation:

• $PPID is the process id of the parent to the current process (the shell executing the current script)
• ps -p gets information on the given process
• grep -v "PID" removes the header line
• awk '{print $4}' gets the fourth column (which is the command name)

Answer 12

echo ${0//-/}

This one returns bash or zsh even if it's a login shell (ie. starting with -).