Start with custom bashrc

[SimonTec]

Hi, I wanted to setup a Singularity container such that a custom bashrc file is executed after entering the container. My current attempts were to use the exec command when calling singularity as follows
singularity exec -B /mnt:/mnt <path_to_container>.sif bash -c "exec bash; source ~/tools/singularity/container_bashrc"
However, the prompt still shows "singularity >". Once in the container, sourcing the container_bashrc works as expected.

This question was asking something similar https://answers.ros.org/question/321775/automatically-source-different-setupbash-files-when-a-starting-singularity-image/. The difference that I see here is that he seemed to build a sandbox from scratch. In my case, I already have a sandbox, and I want to build the sandbox later into a .sif image that is used to run a shell version of the container. Could I add the container_bashrc into the sandbox folder and execute it on start-up with the .run service?