Executing 'bash -c' in 'docker exec' command - bash

Question

Context: I'm trying to write a shortcut for my daily use of the docker exec command. For some reasons, I'm experimenting the problem that my output is sometimes broken when I'm using a bash console inside a container (history messed up, lines overwrite each other as I'm writing, ...)
I read here that you could overcome this problem by adding some command before starting the bash console.
Here is a relevant excerpt of what my script does
#!/bin/bash
containerHash=$1
commandToRun='bash -c "stty cols $COLUMNS rows $LINES && bash -l"'
finalCommand="winpty docker exec -it $containerHash $commandToRun"
echo $finalCommand
$finalCommand
Here is the output I get:
winpty docker exec -it 0b63a bash -c "stty cols $COLUMNS rows $LINES && bash -l"
cols: -c: line 0: unexpected EOF while looking for matching `"'
cols: -c: line 1: syntax error: unexpected end of file
I read here that this had to do with parsing and expansion. However, I can't use a function or an eval command (or at least I didn't succeed in making it work).
If I execute the first output line directly in my terminal, it works without trouble.
How can I overcome this problem?

Answer 1

It's not Docker related, but Bash (In other words, the docker's part of the command works well, it's just bash grumbling on the container like it would grumble on your host):
Minimal reproducible error
cmd='bash -c "echo hello"'
$cmd
hello": -c: line 0: unexpected EOF while looking for matching `"'
hello": -c: line 1: syntax error: unexpected end of file
Fix
cmd='bash -c "echo hello"'
eval $cmd
hello
Answer
foo='docker exec -it XXX bash -c "echo hello"'
eval $foo
This will let you execute your command echo hello on your container, now if you want to add dynamic variables to this command (like echo $string) you just have to get rid of single quotes for double ones, to make this works you will have to escape inner double quotes:
foo="docker exec -it $container bash -c \"echo $variable\""
A complete example
FOO="Hello"
container=$1
bar=$2
cmd="bash -c \"echo $FOO, $bar\""
final_cmd="docker exec -it $container $cmd"
echo "running command: \"$final_cmd\""
eval $final_cmd
Let's take time to dig in,
$FOO is a static variable, in our case it works exactly like a regular variable, just to show you.
$bar is a dynamic variable which takes second command line argument as value
Because $cmd and $final_cmd uses only double quotes, variables are interpreted
Because we use eval $final_cmd command is well interpreted, bash is happy.
Finally, a usage example:
bash /tmp/dockerize.sh 5b02ab015730 world
Gives
running command: "docker exec -it 5b02ab015730 bash -c "echo Hello, world""
Hello, world