README.md in filegen-0.1.1 vs README.md in filegen-0.1.2
- old
+ new
@@ -1,9 +1,10 @@
# Filegen
[](https://travis-ci.org/dg-vrnetze/filegen)
[](https://codeclimate.com/github/dg-vrnetze/filegen)
+[](https://coveralls.io/r/dg-vrnetze/filegen?branch=master)
Have you ever felt the need to generate files based on environment variables or
yaml files? If your answer is yes, then `filegen` can be quite helpful for
you. If your answer is no, than sorry Ma'am, this gem is not for you.
@@ -114,9 +115,42 @@
And get the following result.
```text
Hello my name is: Karl
+```
+
+## Use Cases
+
+### RPM packaging
+
+Say you would like to package a ruby-based application for a rpm-based
+distribution. You can build a rpm package for each gem it depends on or build
+one rpm for the whole application containing all needed gems. After using the
+first approach at first I switched to the second one at last: No need to care
+about different version of one rubygem as dependency of different applications.
+
+To make this possible I decided to use a small wrapper which sets all
+neccessary paths: `GEM_PATH`, `GEM_ROOT` and `GEM_HOME`. After that it executes
+the ruby application. Because every application resists below a different path,
+I needed to generate a different wrapper for each application. For this I use
+this small template:
+
+```erb
+#!/usr/bin/env bash
+
+export GEM_ROOT='<%= lookup('SOFTWARE_LIB') %>'
+export GEM_PATH='<%= lookup('SOFTWARE_LIB') %>'
+export GEM_HOME='<%= lookup('SOFTWARE_LIB') %>'
+
+exec <%= lookup('SOFTWARE_BINARY') %> $*
+```
+
+The wrapper is then generated within the rpm spec:
+
+```
+SOFTWARE_BINARY=<path to rubygems bin> SOFTWARE_LIB=<library_path> filegen gem.erb > <wrapper>
+chmod +x <wrapper>
```
## Future
* Maybe I will add additional data sources. Please see the