How to tell which shell is running a script

Shell Programming and Scripting
1

I've been searching for a while and haven't found this answer anywhere.

How can I tell which shell is running my script from within the script? For example, I have lots of older scripts that we are porting to a new Linux system. Many of the scripts start with ":" alone on a line, which I think long ago forced /bin/sh.

Is there a way to tell within the script what it's being interpreted by? I tried "ps", but that only shows the name of the script.

Thanks,

Sean.

2

Modern shells support the $SHELL variable.

echo $SHELL
3

$SHELL only shows the shell set at login. So if I login, $SHELL = /bin/ksh. If I start a new /bin/sh from my /bin/ksh, $SHELL still = /bin/ksh.

Sean.

4

That doesn't tell you what shell is currently running; it tells you your default shell, which may or may not be your login shell.

5

I always thought that the : in the beginning of a script meant that whatever shell you are in is what the script would use.

I've always found it safer to always specify #!/bin/?shell? at the beginning to make sure.

6

I usually use a shebang only when on a system that doesn't have a POSIX shell in /bin/sh or when I need some feature not supported by the standard shell.

7 
ps -p$$ | xargs -n1 | tail -1

linux:

ps p$$ ocomm h
8

Both of these return the name of the script. If I have a script named test.sh:

#!/bin/sh
ps -p$$ | xargs -n1 | tail -1

or

#!/bin/sh
ps p$$ ocomm h

both return "test.sh". I'm on RHEL 5.3.

I'm hoping to find somethat that will tell me "sh" or "ksh" or whatever shell is actually interpreting the script.

9

It's better to test whether the current shell has the features your script needs.

10

a variation on a theme (tested on Solaris):

#!/bin/ksh

echo "myShell->[$(ps -o 'pid,comm' -p "${$}" | xargs -n1 | tail -1)]"
# OR
# echo "myShell->[$(ps -o comm -p "$$" | { read; read comm; echo "$comm"; })]"
11

This works for me on AIX, but on Linux it always returns:

myShell->[test.sh]

12

I don't have linux in front of me, but most likely it should be a combination of what you do on above with what 'Scrutinizer' suggested previously.
Maybe others could 'port' this to linux for you.

13

This should work in RHEL 5.3:

#!/bin/sh
comm=$(ps -p $$ -o command h|cut -d' ' -f1)
shell=${comm##*/}
echo $shell