Hi, I have a question on the behavior of the new array PROMPT_COMMANDS
and the best practice to use it.
In coming Bash 5.1, the new array variable `PROMPT_COMMANDS' is
available in the replacement of `PROMPT_COMMAND'. When the array
`PROMPT_COMMANDS' has one or more elements, the scalar version
`PROMPT_COMMAND' is disabled.
Is there a background that the scalar version is disabled in the
presence of the array version? Because of this behavior, I am
wondering how to write a source script in the way not interfering with
other source scripts which might use either of `PROMPT_COMMANDS' or
`PROMPT_COMMAND'.
* If I use the newer form `PROMPT_COMMANDS+=(my-function)', other
scripts that use `PROMPT_COMMAND' will be broken. Maybe I can write
in the following way to convert `PROMPT_COMMAND' to
`PROMPT_COMMANDS', but it still does not resolve the problem of the
scripts sourced after my script.
if [[ $PROMPT_COMMAND ]]; then
PROMPT_COMMANDS+=("$PROMPT_COMMAND")
unset PROMPT_COMMAND
fi
PROMPT_COMMANDS+=(my-function)
* If I use the older form with `PROMPT_COMMAND', it will be broken
when another script sets the variable `PROMPT_COMMANDS'. Maybe I
can switch to `PROMPT_COMMANDS' only when the array already exists,
but it again does not work when the other script sourced after mine
newly sets `PROMPT_COMMANDS'.
if ((${#PROMPT_COMMANDS})); then
PROMPT_COMMANDS+=(my-function)
else
PROMPT_COMMAND="my-function${PROMPT_COMMAND:+;}$PROMPT_COMMAND"
fi
Here, my question is what is the best practice to use the new array
variable `PROMPT_COMMANDS' in the way that it does not break the
conventional scripts that use `PROMPT_COMMAND'.
# The related commit is 5f49ef47d (commit bash-20200323 snapshot).
# Here are the related threads:
# https://lists.gnu.org/archive/html/bug-bash/2018-01/threads.html#00067
# https://lists.gnu.org/archive/html/bug-bash/2018-02/threads.html#00019
--
Koichi
