How to define pwd as a variable in Unix shell

try this:

dir="$PWD"

or

dir="$(pwd)"

you may want to have double quotes too if your path contained special chars, like spaces.

The current directory is already in a variable, called PWD, and it is automatically set by the shell:

echo "$PWD"

You could also:

dir=$(pwd)
echo "$dir"

Or you could use these in your script without storing in additional variables:

/bin/env/####/ --id --edition-dir "$PWD"
/bin/env/####/ --id --edition-dir "$(pwd)"

For your information: every time you change directory, whether in an interactive shell or a script, the shell sets the value of the PWD variable to the current directory, and the value of OLDPWD to the previous directory.

Well, usually. As @WilliamPursell pointed out, OLDPWD is not standard, so it might not be available in all shells.