sh man page ....

[RW]

On Fri, 10 Oct 2014 19:10:03 -0500
William A. Mahaffey III wrote:


> Straight out of the script which is failing. Under linux, if I call
> the script w/ no '-s #' option, the variable 'slept' is not set, &
> linux (or more accurately linux bash) evaluates that to the value oif
> zero (0).
> 
> 
> [wam at kabini1, ~, 7:07:22pm] 386 % sh
> $ if [ 0 -lt $(($slept)) ] ; then echo -n "$cmd: sleeping $slept secs 
> ...." ; sleep $(($slept)) ; echo " done." ; fi
> arithmetic expression: expecting primary: ""
> [wam at kabini1, ~, 7:07:45pm] 387 %


The problem here is that you have:

  [ 0 -lt $(($slept)) ] 

If you change it to the normal usage

  [ 0 -lt $((slept)) ]

it works as expected.

Is there any particular reason for the extra "$"?

I guess the difference is not in the handling of uninitialised
variables, but specifically in the handling of $(()) which is an error
in sh, but not is bash.