let and typeset
let is an alternative to expr for doing mathematical calculations. It is part of the posix shell and is similiar to the C programming statement e.g.
will add one to $TOTAL This can be alternatively expressed as
(( $TOTAL = $TOTAL + 1 ))
To speed up the arithmetic calculation you can specify that $TOTAL is a number. This is done as follows:
typset -i TOTAL=10
Another use of typeset is to emulate the substring function found in other languages. e.g.
typeset -L4 var1="12345678" will set var1 to 1234 typeset -R4 var2="12345678" will set var2 to 5678
The string 12345678 can be replaced by a variable.