Recipe 15-2: RPM Report
This recipe does a useful task in that it compares RPMs installed on different machines and produces a reasonably easy-to-read report on the findings. This is often made more difficult by the way that RPM filenames work: a dash is a valid (and fairly common) part of the package name, as well as being used to separate the name, version, and release from one another.
This report takes the output from the rpm -qa command as input, which can be run on multiple different machines, or on the same machine at different times, to see how the package list compares either between machines or over time, respectively. Packages that are the same across all input files are shown as black text on a white background. Packages that have a variety of different versions installed are shown on a gray background for easy identification.
- Parameter expansion, in particular % and ##
- Associative arrays (these only work in bash version 4 or later)
- Here documents
RPM filenames contain a lot of information but are not particularly easy to parse. For example, gnome-panel-2.16.1-7.el5 is version 2.16.1 of the software, but release number 7.el5 of that version. Because parts of the filename are split with hyphens, and hyphens are quite common in package names, it becomes difficult to work out what part of the filename is what. The only way to do it is to work from the back; the version and release fields cannot contain hyphens. This means that ...