Issue passing variable into shell script

Question

Please see terminal session.
-  calling pwd, unset, or echo alleviate the issue.
- running the script 'plain' also exihibit an issue
- calling 'cat test.sh' causes an issue
I can repeat the issue on OSX 10.5.8
On Ubuntu, two a's always print out with: A=a B=$A ./test.sh
Terminal session:
bash-3.2$ ls -l test.sh
-rwxr-xr-x  1 axure  staff  16 Mar 29 09:27 test.sh
bash-3.2$ cat test.sh
echo $A
echo $B
bash-3.2$ pwd
/Users/axure
bash-3.2$ A=a B=$A ./test.sh
a
a
bash-3.2$ A=a B=$A ./test.sh
a
bash-3.2$ $A
bash-3.2$ $B
bash-3.2$ echo $A
bash-3.2$ echo $B
bash-3.2$ unset
bash-3.2$ A=a B=$A ./test.sh
a
a
bash-3.2$ A=a B=$A ./test.sh
a
bash-3.2$ pwd
/Users/axure
bash-3.2$ A=a B=$A ./test.sh
a
a
bash-3.2$ A=a B=$A ./test.sh
a
bash-3.2$ unset
bash-3.2$ cat test.sh
echo $A
echo $B
bash-3.2$ A=a B=$A ./test.sh
a
bash-3.2$ unset
bash-3.2$ A=a B=$A ./test.sh
a
a
bash-3.2$ A=a B=$A ./test.sh
a
bash-3.2$ unset
bash-3.2$ ./test.sh
bash-3.2$ A=a B=$A ./test.sh
a
bash-3.2$

Answer 1

bash-3.2$ ls -l test.sh
-rwxr-xr-x  1 axure  staff  16 Mar 29 09:27 test.sh
bash-3.2$ cat test.sh
echo $A
echo $B
bash-3.2$ pwd
/Users/axure
bash-3.2$ A=a B=$A ./test.sh
a
a
As I would expect
bash-3.2$ A=a B=$A ./test.sh
a
NOT what I would expect.  I tested this using bash 3.2 and got the same results, HOWEVER, when I tested this with bash 4.0, I got what I expected, namely your first results everytime.
So I think there is a bug in bash 3.2.  You can get the bash sources, and build your own bash if you wish, or use a different method of setting 1 time envionment variables for use in a subprocess.
bash-3.2$ $A
bash-3.2$ $B
bash-3.2$ echo $A
bash-3.2$ echo $B
As expected, as the way you set A & B were as 1 time environment variables that were only seen by the subprocess created when test.sh was run.  A & B were NOT created in the current shell environment, so the current shell environment would not have any values for A & B
bash-3.2$ unset
bash-3.2$ A=a B=$A ./test.sh
a
a
bash-3.2$ A=a B=$A ./test.sh
a
Again, now what I would expect, but as I have already stated, I think there is a bug in bash 3.2 that does not exist in bash 4.0.
Now a bigger question, why are you passing A & B as 1 time envionment variables?  Why not just pass them on the command line?
test.sh a a
where test.sh would be
echo $1
echo $2
Or you could use export to create environment variables A & B
export A=a
export B=$A
test.sh
Now A & B would still exist after test.sh, which I assume you do not want to do.
You could try ceating test.sh as a bash function and see if that changes the behavior
test()
    echo $A
    echo $B
A=a B=$A test
You would have to define test() in your shell initialization scirpt if you needed each time you started a terminal session.
While I have used 1 time environment variables, I more frequently just pass arguments on the command line.