Consider binaries to implement the functionality offered by `gz`

[osrf-migration]

Original report (archived issue) by Carlos Agüero (Bitbucket: caguero, GitHub: caguero).

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Right now, ign is a ruby script that offers several subcommands (topic, msg, etc.). Each subcommand is implemented by a function inside a versioned Ignition shared library. ign also keeps track of multiple versions of the same library. This approach has some issues, in particular we have detected:

1. Difficulty for using gdb when running ign. Imagine for example running ign gazebo …
2. Portability issues. E.g.: On Windows, there are ABI problems interacting from Ruby (compiled with MinGW) and an Ignition shared library (compiled with Visual Studio).

An idea for mitigating these issues might be to move the functionality from a shared library to a binary (e.g.: igntopic). In this case, ign should invoke the right external binary. The solution to (1) is to run gdb with the binary directly without using ign. (2) probably won’t happen again as we wouldn’t need to interact with a shared library anymore, just executing an external binary which looks less involved.

On the other hand, each Ignition library should do some refactor and expose a binary (or a collection of binaries) that capture all functionality to be executed from the command line.

‌

• gz-transport
  • Add standalone executables gz-transport#216
  • Add standalone executable for ign-transport-log command gz-transport#247
  • gz param (parameters/src/cmd/cmdparam.rb.in)
• gz-msgs Support standalone executable in gz-msgs11 gz-msgs#357
• gz-gui
  • Add standalone executable gz-gui#250
• gz-launch
  • Add standalone executables gz-launch#121
• gz-fuel-tools (src/cmd/cmdfuel.rb.in)
• gz-plugin
  • Add standalone executable for ign-plugin-info command gz-plugin#54
  • Added standalone executable gz-plugin#65
• gz-sim
  • Standalone Ignition Gazebo executables gz-sim#694
  • Standalone gz sim executable (Jetty) gz-sim#2849
  • Fix for GUI wait screen bug in standalone executable gz-sim#2905
• sdformat
  • WIP: Implement gz sdf as standalone executable sdformat#1465
  • Standalone gz sdf executable sdformat#1539

[chapulina]

ign-tools itself should not be limited to loading shared libraries right now. This is being done at each library's Ruby file, for example cmdtransport.rb.in.

To use executables in ign-transport for example, one would need to:

• Install executables that provide the command line functionality, like topic and service
• Call those from the Ruby script instead of loading a shared lib
• It may be interesting to move the command line argument parsing from Ruby to the executables