# Trying to run NASA GMAT on Ubuntu 20.04, I get the error "no main manifest attribute, in gmat.jar"

I downloaded GMAT from https://software.nasa.gov/software/GSC-17177-1
Then I extracted using tar -zxf gmat-ubuntu-x64-R2020a.tar.gz
Then I went to the bin folder and set gmat.jar as an executable (rightclick -> properties -> permissions).
Finally when I tried java -jar gmat.jar, I get

no main manifest attribute, in gmat.jar

• Note to potential close voters: software questions about certain topics (e.g. for anything space or orbital mechanics related and certainly anything GMAT-related) have always been on-topic here! While some are also on-topic in Stack Overflow, there are GMAT users here who may be familiar with just this case. If no answers arise, this can always be moved to SO later.
– uhoh
Sep 18 at 15:20
• I'm not able to try this out myself at the moment, but looking at sourceforge.net/projects/gmat/files/GMAT/GMAT-R2016a it appears to me that it is not intended to be run directly from the jar. Likely the jar manifest does not include Main-Class:  . You can confirm by extracting the jar as a zip file and looking at the text of META-INF/MANIFEST.MF. Try running GmatConsole or Gmat_Beta instead as a regular executable Sep 18 at 16:12

GMAT is written primarily in C++.

gmat.jar is an api wrapper to allow java code to access the core functionality as explained at http://gmat.sourceforge.net/docs/R2020a/api/userguide/GettingStarted.html

In other words, gmat.jar would be used if you wanted to write your own java program that interacted with gmat functionality.

Running the gmat application is explained at https://sourceforge.net/projects/gmat/files/GMAT/GMAT-R2016a/

On Linux, open a terminal window and change directories to the GMAT bin folder. The GMAT command line program is executed by running the GmatConsole application in that folder:

./GmatConsole

The Beta GUI can be run using the same terminal window by running Gmat_Beta:

./Gmat_Beta

Linux users can create a launcher for either the command line application or the GUI application by following the instructions for that process for their Linux distribution.

# Version Notes

The links from the NASA page to the sourceforge link can be a bit confusing. To make sure you are getting the instructions for the version you are downloading, navigate through https://sourceforge.net/projects/gmat/files/GMAT/ to the version you want to use.

UBUNTU 18.04 Note: Ubuntu 18.04 does not ship with libpng12.so, used by the wxWidgets libraries bundled with the Ubuntu installation. You can download the needed library from the Ubuntu packages site