Perl keeps track of online orders


The script needs the Sysadm::Install, Cache::FileCache, DateTime, and DateTime::Format::Strptime modules from CPAN, which are best installed by way of a CPAN shell to resolve dependencies automatically. Alternatively, you can use your Linux package manager if its repository has all of the required modules on hand. Their names might be slightly different in this case, though: libsysadm-install-perl, for example, is Debian's idea of Sysadm::Install.

Before you start, you will need to set up an empty server-side repository manually with the use of git init (Figure 2). Perl modules are not required on the hosted machine; however, you do need the git program, but it is part of most of today's Linux systems anyway.

Figure 7 shows how the first client initializes its local repository, uses shop buy to enter a couple of purchases, runs shop list to query the local database, and ultimately transfers data to the server with shop push. The shop commands do not produce any output if they run successfully.

Figure 7: The first client creates the local repository, populates it with data, and then updates the previously empty server repository.

The second client then uses shop clone to create a local clone of the server repository, as shown in Figure 8. That client also makes a couple of purchases and tags the iPod Nano transaction with Amazon as complete. It then issues a shop push to push the local changes to the server.

Figure 8: The second client retrieves the data from the server repository, adds new data, and pushes new entries to the server.

The same procedure applies to all further clients; again, they first clone the server repository, make some changes to the local repository, push the new data to the server, and receive the latest updates from the other clients via a server pull. The feast of orders can go on and on, and thankfully, Git will notice immediately any deliveries that fail to reach their destination because of mail problems or supplier sloppiness.


  1. Listings for this article:
  2. Swicegood, Travis. Pragmatic Version Control Using Git. Pragmatic Bookshelf, 2008

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