In Visual Studio you can add an external tool and pass it the selected text as parameter.
Does eclipse have the same kind of feature or are one obliged to code a plugin for that ?
If so, any specific code sample to do just that because all I found is general sample plugin for custom editor.
Sure, they are even called "External Tools". look in Run->External Tools.
Actually, start by typing "External Tools" into the Eclipse Help search box.
Eclipse has the kitchen sink, do you think they would leave this out? :-)
As a side note might be added, that the possibility to add external tools was one of the key features of the eclipse platform once it was brought up back in the days. VisualAge had a big problem with external tools.