doas doesn't work with [[ in bash

[peterwu]

$ [ -e ~/testfile ]        # good
$ [[ -e ~/testfile ]]      # good
$ doas [ -e ~/testfile ]   # good
$ doas [[ -e ~/testfile ]] # error below
doas: [[: command not found

[Duncaen]

[[ is a bash builtin, [ also exists as binary, doas does not know or try to attempt to execute commands it can't find in PATH in a shell.

You'll have to explicitly run it in a bash shell if you want to do this: doas bash -c '[[ -e ~/testfile ]]'.