''bash :root: command not found'' ERROR

Dear Rooters,

I'm a novice user and I have stupid question. I have installed root for analysing PLANTOCOSMICS outputs. I didn't get any error message during installation.But when I type the command '' root myfilename.root '' I will get the following error

bash :root: command not found

Do you think that I didn't set the enviroment variable correctly or is there other problem?

Thanks in advance.
cheers

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Farzaneh