math programming help in shell
 

i am trying to do some math for a program, and i am getting an error. here is my code:
let perimeter=2*$l+2*$w

error:
rectangle: line 6: let: perimeter=2*: syntax error: operand expected (error token is "*")

show us the entire script please.
[code][/code] tags Please.
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http://www.tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html
http://www.tldp.org/LDP/Bash-Beginne...tml/index.html
http://www.gnu.org/software/bash/man...ode/index.html
http://www.grymoire.com/Unix/Sh.html
http://tldp.org/LDP/abs/abs-guide.pdf
http://www.tldp.org/LDP/abs/html/
http://mywiki.wooledge.org/BashFAQ
http://mywiki.wooledge.org/BashPitfalls

The shell is not very good at doing math directly, but you can use other programs for this, such as bc.

Regular expressions ...

See;
http://www.freeos.com/guides/lsst/ch02sec07.html

You have to use escape characters to preserve mathematical functions...