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Date: Wed, 4 Dec 1996 16:52:06 +0800 (CST)
To: questions@freebsd.org
Subject: shell programming
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Hi,

I want to calculate intergers under Bourne Shell, I input the following:

a=10 <enter>
a='expr $a+10' <enter>

when I typed "echo $a", the result from system is "expr $a+1" just the 
same as I typed it in the command, but as the "expr' manul says, the result 
should be "20", what's the problem? 

Further more, I want to know a general way to do some calculation using 
variables under unix shell.

Thanks in advance!

Song