We use `trap` to bootstrap our installation function (__bp_install). We
remove our code upon first execution but need to restore any preexisting
trap calls. We previously used `sed` to process the trap string, but
that had two downsides:
1. `sed` is an external command dependency. It needs to exist on the
system, and we need to invoke it in a subshell (which has some runtime
cost).
2. The regular expression pattern was imperfect and didn't handle
trickier cases like `'` characters in the trap string:
$ (trap "echo 'hello'" DEBUG; trap -p DEBUG)
hello
trap -- 'echo '\''hello'\''' DEBUG
This change removes the dependency on `sed` by locally evaluating the
trap string and extracting any prior trap. This works reliably because
we control the format our trap string, which looks like this (with
newlines expanded):
__bp_trap_string="$(trap -p DEBUG)"
trap - DEBUG
__bp_install
Upstream: https://github.com/rcaloras/bash-preexec/pull/170
We use `trap` to bootstrap our installation function (__bp_install). We
remove our code upon first execution but need to restore any preexisting
trap calls. We previously used `sed` to process the trap string, but
that had two downsides:
1. `sed` is an external command dependency. It needs to exist on the
system, and we need to invoke it in a subshell (which has some
runtime cost).
2. The regular expression pattern was imperfect and didn't handle
trickier cases like `'` characters in the trap string:
$ (trap "echo 'hello'" DEBUG; trap -p DEBUG)
hello
trap -- 'echo '\''hello'\''' DEBUG
This change removes the dependency on `sed` by locally evaluating the
trap string and extracting any prior trap. This works reliably because
we control the format our trap string, which looks like this (with
newlines expanded):
__bp_trap_string="$(trap -p DEBUG)"
trap - DEBUG
__bp_install
We post-process history 1's output to extract the current command. This
processing needs to strip the leading history number, an optional *
character indicating whether the entry was modified (or a space), and
then a space separating character.
We were previously using sed(1) for this, but we can implement an
equivalent transformation using bash's native parameter expansion
syntax.
This also results in ~4x reduction in per-prompt command overhead.
