Shell Programming and Scripting

Hello
My question is: How to find out the shell of the shell script which we are running? I am writing a script, say f1.sh, as below:

Code:

#!/bin/ksh

echo "Sample script"

From the first line, we can say this script will run in ksh. But, how can we prove it? Can we print anything inside the script to verify it? echo $SHELL wont help since it will show the login shell which in my case is bash. echo $0 also wont help since $0 in this case will be the name of the script. The ps command does not help. It will show the name of the script in the process list, not the shell as such.

Please advice.

i created a test.sh with the below contents and just executed it.

Code:

$ cat test.sh      
#!/bin/ksh
echo $SHELL
echo $0
while [ 1 ]
do
    sleep 5;
done

after that, i tried one more terminal and did the below command

Code:

ps -ef | grep test

the output of the above commands shows that the shell script was executed with the ksh

Code:

$ ps -ef | grep test
 kamaraj 20943  4832   0 06:24:44 pts/10      0:00 grep test
 kamaraj 20936 13784   0 06:24:32 pts/11      0:00 /bin/ksh ./test.sh

---------- Post updated at 12:00 PM ---------- Previous update was at 11:59 AM ----------

my default shell was

Code:

 
$ echo $SHELL
/usr/bin/bash

and the echo $SHELL was printed the /bin/bash

Code:

#!/bin/ksh
p="${0/.\//}"
ps -ef|awk -vp="$p" '!/awk/&&/'$p'/{print "Script is in the -> " $(NF-1)}'
sleep 1

Code:

# ./check
Script is in the -> /bin/ksh

The very fact that the first line (#! /bin/ksh) is interpreted without errors proves that it is on ksh.

If you tried to use hello shell (any non-existent shell) - #! /bin/hello, it would throw an error: -bash: ./test.sh: /bin/hello: bad interpreter: No such file or directory, right.

@balajesuri: I think you did not get my question. My question is not whether the shell in the shebang line is a valid ksh or not. The question is say if you are asked in which shell your script is running, how to confirm or prove it?


@ygemici,itkamaraj: thanks..

I understood your question. What I'm saying is, if the shebang line (#! /bin/ksh) is interpreted without errors, isn't that a sufficient proof that it is indeed on ksh?

The full comprehensive and exhaustive answer to this question is on the excellent Mascheck site.

what shell is this