I'm trying to imagine why you care whether the user views all the output...

But anyhow, what if the user enters Q or Ctrl-C or Ctrl-Z or ! pkill more?

Update: 

   $ man more
   EXIT STATUS
     The following exit values are returned:

     0     Successful completion.

     >0    An error occurred.
    --More--(90%)

[download]

And (at least) the following are considered successful completion:

In reply to Re: How to know whether user terminates system("$cmd|more") with q or not? by hbm
in thread How to know whether user terminates system("$cmd|more") with q or not? by PerlOnTheWay

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