Shell Programming and Scripting

Methyl, it is not the same problem as the previous one.
In the previous case, the script was executed from cygwin terminal in win xp environment. But now I was trying to run the script from linux terminal in Ubuntu env.
I guess the problem might be due to some shell related or setting problem. As I am new to linux, can't figure out the exact problem.
I will post the output of the command once I execute the command in my ubuntu laptop. Thank you.

How are you calling the script? If you call it for example as sh ./script then the shebang is ignored and you are using /bin/sh , which is dash on Ubuntu, not bash....

I was calling the script as sh scriptname

Right, then that explains it. So you would need to use ./scriptname or bash ./scriptname..

@linux_learner
When posting a problem please state what Operating System and version you are running and what Shell you are using. Every time.
When you have a problem please post the script intact (blotting anything confidential with X's) and any error messages verbatim.
If there is a question about different environments please post the output from the command set for both the environment which works and the environment which does not work. Just doing this will often make the solution obvious to you. Sometimes a cron containing just set will reveal the problem.

Back on topic.
Srutinizer has cracked it. You ran a "bash" Shell in a "dash" environment. This was unguessable based on the information originally posted.
Now if you had posted the exact error messages verbatim?

The main lesson here is that "bash" has many extensions to scripting language which are really useful but which do not work at all in normal unix Shells.

When you get an error message, post the error message 100% accurately case-significant and with every space character intact.
There is no Shell which outputs "no such commands" or "invalid option with the command" but there are some which output "syntax error" but probably not in lower-case.

Thanks methyl and Scrutinizer, now it is clear to me and it is working as expected.

@Scrutinizer, could you please explain me how to check which shell is being used when I am running some script in Ubuntu? If I run the command echo $SHELL, it displays /bin/bash, so I thought the script was run in bash shell.

Thanks in advance.

Hi linux_learner, sh script means that /bin/sh will be used to execute the script, overriding any shell that is specified on the first line in the script that starts with #!
Historically /bin/sh was the Bourne Shell, on modern systems /bin/sh usually means a POSIX shell, with a limited set of features of what bash offers. So if you use sh, you should limit yourself to the POSIX feature set. On many linuxen /bin/sh this is a link to /bin/bash and if bash gets called this way it conforms to POSIX more closely, but not fully ( for example read -n still works ). On Ubuntu /bin/sh is linked to /bin/dash, which is a very fast shell that is pretty near a POSIX shell and not much else..