Bulk password changes

I recently had to create a batch of new user account under Linux. I already had a nice script for generating a hard password but I needed to set them on mass. Reading man passwd I found the section about using it in a script:

--stdin
       This option is used to indicate that passwd should read the  
       new password from standard input, which can be a pipe.

When I tried to use it I got this error:

pass="jjhjhjhg"
user="testbob"
echo $pass | passwd –-stdin "$user"
passwd: Only one user name may be specified.

In the end I found another program to do it for me:

echo "$user:$pass" | chpasswd