If you'd like to download iSync 2.1 with the softwareupdate command-line tool, make sure that your current working directory is at the root level of the startup volume (you should be at /). You can then use the softwareupdate tool to get iSync 2.1.
Note: iSync 2.1 requires Mac OS X 10.4 or later. It will not appear in Mac OS X 10.3.9 or earlier.
To see if this update is available for the computer via softwareupdate, execute these commands:
$ cd /
$ sudo softwareupdate -l
To install iSync 2.1 using the softwareupdate command-line tool, execute the following two commands:
$ cd /
$ sudo softwareupdate -i iSync\ 2.1
To install software updates with softwareupdate, you must run the command with sudo or as the root user. Be sure to include the backslash (\) character in "iSync\ 2.1" so that softwareupdate correctly interprets the space in the file name. Backslash is also known as "reverse solidus".
If you want to use Software Update (part of System Preferences—from the Apple menu, choose Software Update) to download iSync 2.1 instead of using softwareupdate, you needn't worry about what your current working directory is.
To learn more about this tool, type man softwareupdate in Terminal.