A simple custom command for starship to detect if a shell is in a distrobox container.

starship.toml

### use it in your starship.toml
# in the top include it in your main format using ${custom.distrobox} (with brackets)
# format = " .... ${custom.distrobox}  ..."


[custom.distrobox]
description = "Displays name of the activated distrobox container"
# box symbol from NerdFonts
symbol = " "

# activates when the command in "when" returns 0 (succeed / true)
# we check for the $CONTAINER_ID variable as described in https://github.com/89luca89/distrobox/blob/main/docs/useful_tips.md#detect-if-youre-in-a-distrobox
when = "[[ ! -z \"${CONTAINER_ID}\" ]]"

# the output of this command will be provided in $output for the format
# here we get the name of the distrobox
command = "echo ${CONTAINER_ID}"

# format in the shell
format = "[ $symbol $output ]($style)"

disabled = false

# apply your favorite style here...
style = "bold green"

Could look like this: