faul_sname comments on Process Substitution Without Shell?

[faul_sname]

And since I use a string to build up CMD it now means all of the arguments need to be well behaved.

I’m not entirely sure what you mean by that—it looks like you’re already using arrays instead of string concatenation to construct your command on the python side and properly quoting shell args on the bash side, so I wouldn’t expect you to run into any quoting issues.

[jefftk]

I have CMD+=" -S $1", so if $1 has any spaces in it the parsing will be wrong.

Now, I know this about my script and will be careful not to do that, but it’s still a risk.

[faul_sname]

Ah, I see.

It may be worthwhile to instead define CMD as an array, rather than a string, like this

CMD=("do_some_thing")
if [[ "$USE_S_FLAG" == 1 ]]; then
    CMD+=("-S", "$1")
fi
"${CMD[@]}" "the" "rest" "of" "your" "args"

Of course at that point you’re losing some of the readability benefits of using bash in the first place...

Edit: or, of course, you keep the script simple and readable at the cost of some duplication, e.g.

if [[ "$USE_S_FLAG" == 1 ]]; then
   "$CMD" -S "$1" "the" "rest" "of" "your" "args"
else
   "$CMD" "the" "rest" "of" "your" "args"
fi