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bash-preexec.sh
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bash-preexec.sh
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# bash-preexec.sh -- Bash support for ZSH-like 'preexec' and 'precmd' functions.
# https://github.com/rcaloras/bash-preexec
#
#
# 'preexec' functions are executed before each interactive command is
# executed, with the interactive command as its argument. The 'precmd'
# function is executed before each prompt is displayed.
#
# Author: Ryan Caloras ([email protected])
# Forked from Original Author: Glyph Lefkowitz
#
# V0.5.0
#
# General Usage:
#
# 1. Source this file at the end of your bash profile so as not to interfere
# with anything else that's using PROMPT_COMMAND.
#
# 2. Add any precmd or preexec functions by appending them to their arrays:
# e.g.
# precmd_functions+=(my_precmd_function)
# precmd_functions+=(some_other_precmd_function)
#
# preexec_functions+=(my_preexec_function)
#
# 3. Consider changing anything using the DEBUG trap or PROMPT_COMMAND
# to use preexec and precmd instead. Preexisting usages will be
# preserved, but doing so manually may be less surprising.
#
# Note: This module requires two Bash features which you must not otherwise be
# using: the "DEBUG" trap, and the "PROMPT_COMMAND" variable. If you override
# either of these after bash-preexec has been installed it will most likely break.
# Tell shellcheck what kind of file this is.
# shellcheck shell=bash
# Make sure this is bash that's running and return otherwise.
# Use POSIX syntax for this line:
if [ -z "${BASH_VERSION-}" ]; then
return 1;
fi
# We only support Bash 3.1+.
# Note: BASH_VERSINFO is first available in Bash-2.0.
if [[ -z "${BASH_VERSINFO-}" ]] || (( BASH_VERSINFO[0] < 3 || (BASH_VERSINFO[0] == 3 && BASH_VERSINFO[1] < 1) )); then
return 1
fi
# Avoid duplicate inclusion
if [[ -n "${bash_preexec_imported:-}" || -n "${__bp_imported:-}" ]]; then
return 0
fi
bash_preexec_imported="defined"
# WARNING: This variable is no longer used and should not be relied upon.
# Use ${bash_preexec_imported} instead.
# shellcheck disable=SC2034
__bp_imported="${bash_preexec_imported}"
# Should be available to each precmd and preexec
# functions, should they want it. $? and $_ are available as $? and $_, but
# $PIPESTATUS is available only in a copy, $BP_PIPESTATUS.
# TODO: Figure out how to restore PIPESTATUS before each precmd or preexec
# function.
__bp_last_ret_value="$?"
BP_PIPESTATUS=("${PIPESTATUS[@]}")
__bp_last_argument_prev_command="$_"
__bp_inside_precmd=0
__bp_inside_preexec=0
# Initial PROMPT_COMMAND string that is removed from PROMPT_COMMAND post __bp_install
__bp_install_string=$'__bp_trap_string="$(trap -p DEBUG)"\ntrap - DEBUG\n__bp_install'
# Fails if any of the given variables are readonly
# Reference https://stackoverflow.com/a/4441178
__bp_require_not_readonly() {
local var
for var; do
if ! ( unset "$var" 2> /dev/null ); then
echo "bash-preexec requires write access to ${var}" >&2
return 1
fi
done
}
# Remove ignorespace and or replace ignoreboth from HISTCONTROL
# so we can accurately invoke preexec with a command from our
# history even if it starts with a space.
__bp_adjust_histcontrol() {
local histcontrol
histcontrol="${HISTCONTROL:-}"
histcontrol="${histcontrol//ignorespace}"
# Replace ignoreboth with ignoredups
if [[ "$histcontrol" == *"ignoreboth"* ]]; then
histcontrol="ignoredups:${histcontrol//ignoreboth}"
fi;
export HISTCONTROL="$histcontrol"
}
# This variable describes whether we are currently in "interactive mode";
# i.e. whether this shell has just executed a prompt and is waiting for user
# input. It documents whether the current command invoked by the trace hook is
# run interactively by the user; it's set immediately after the prompt hook,
# and unset as soon as the trace hook is run.
__bp_preexec_interactive_mode=""
# These arrays are used to add functions to be run before, or after, prompts.
declare -a precmd_functions
declare -a preexec_functions
# Trims leading and trailing whitespace from $2 and writes it to the variable
# name passed as $1
__bp_trim_whitespace() {
local var=${1:?} text=${2:-}
text="${text#"${text%%[![:space:]]*}"}" # remove leading whitespace characters
text="${text%"${text##*[![:space:]]}"}" # remove trailing whitespace characters
printf -v "$var" '%s' "$text"
}
# Trims whitespace and removes any leading or trailing semicolons from $2 and
# writes the resulting string to the variable name passed as $1. Used for
# manipulating substrings in PROMPT_COMMAND
__bp_sanitize_string() {
local var=${1:?} text=${2:-} sanitized
__bp_trim_whitespace sanitized "$text"
sanitized=${sanitized%;}
sanitized=${sanitized#;}
__bp_trim_whitespace sanitized "$sanitized"
printf -v "$var" '%s' "$sanitized"
}
# This function is installed as part of the PROMPT_COMMAND;
# It sets a variable to indicate that the prompt was just displayed,
# to allow the DEBUG trap to know that the next command is likely interactive.
__bp_interactive_mode() {
__bp_preexec_interactive_mode="on";
}
# This function is installed as part of the PROMPT_COMMAND.
# It will invoke any functions defined in the precmd_functions array.
__bp_precmd_invoke_cmd() {
# Save the returned value from our last command, and from each process in
# its pipeline. Note: this MUST be the first thing done in this function.
# BP_PIPESTATUS may be unused, ignore
# shellcheck disable=SC2034
__bp_last_ret_value="$?" BP_PIPESTATUS=("${PIPESTATUS[@]}")
# Don't invoke precmds if we are inside an execution of an "original
# prompt command" by another precmd execution loop. This avoids infinite
# recursion.
if (( __bp_inside_precmd > 0 )); then
return
fi
local __bp_inside_precmd=1
# Invoke every function defined in our function array.
local precmd_function
for precmd_function in "${precmd_functions[@]}"; do
# Only execute this function if it actually exists.
# Test existence of functions with: declare -[Ff]
if type -t "$precmd_function" 1>/dev/null; then
__bp_set_ret_value "$__bp_last_ret_value" "$__bp_last_argument_prev_command"
# Quote our function invocation to prevent issues with IFS
"$precmd_function"
fi
done
__bp_set_ret_value "$__bp_last_ret_value"
}
# Sets a return value in $?. We may want to get access to the $? variable in our
# precmd functions. This is available for instance in zsh. We can simulate it in bash
# by setting the value here.
__bp_set_ret_value() {
return ${1:+"$1"}
}
__bp_in_prompt_command() {
local prompt_command_array IFS=$'\n;'
read -rd '' -a prompt_command_array <<< "${PROMPT_COMMAND[*]:-}"
local trimmed_arg
__bp_trim_whitespace trimmed_arg "${1:-}"
local command trimmed_command
for command in "${prompt_command_array[@]:-}"; do
__bp_trim_whitespace trimmed_command "$command"
if [[ "$trimmed_command" == "$trimmed_arg" ]]; then
return 0
fi
done
return 1
}
# This function is installed as the DEBUG trap. It is invoked before each
# interactive prompt display. Its purpose is to inspect the current
# environment to attempt to detect if the current command is being invoked
# interactively, and invoke 'preexec' if so.
__bp_preexec_invoke_exec() {
# Save the contents of $_ so that it can be restored later on.
# https://stackoverflow.com/questions/40944532/bash-preserve-in-a-debug-trap#40944702
__bp_last_argument_prev_command="${1:-}"
# Don't invoke preexecs if we are inside of another preexec.
if (( __bp_inside_preexec > 0 )); then
return
fi
local __bp_inside_preexec=1
# Checks if the file descriptor is not standard out (i.e. '1')
# __bp_delay_install checks if we're in test. Needed for bats to run.
# Prevents preexec from being invoked for functions in PS1
if [[ ! -t 1 && -z "${__bp_delay_install:-}" ]]; then
return
fi
if [[ -n "${COMP_POINT:-}" || -n "${READLINE_POINT:-}" ]]; then
# We're in the middle of a completer or a keybinding set up by "bind
# -x". This obviously can't be an interactively issued command.
return
fi
if [[ -z "${__bp_preexec_interactive_mode:-}" ]]; then
# We're doing something related to displaying the prompt. Let the
# prompt set the title instead of me.
return
else
# If we're in a subshell, then the prompt won't be re-displayed to put
# us back into interactive mode, so let's not set the variable back.
# In other words, if you have a subshell like
# (sleep 1; sleep 2)
# You want to see the 'sleep 2' as a set_command_title as well.
if [[ 0 -eq "${BASH_SUBSHELL:-}" ]]; then
__bp_preexec_interactive_mode=""
fi
fi
if __bp_in_prompt_command "${BASH_COMMAND:-}"; then
# If we're executing something inside our prompt_command then we don't
# want to call preexec. Bash prior to 3.1 can't detect this at all :/
__bp_preexec_interactive_mode=""
return
fi
local this_command
this_command=$(
export LC_ALL=C
HISTTIMEFORMAT='' builtin history 1 | sed '1 s/^ *[0-9][0-9]*[* ] //'
)
# Sanity check to make sure we have something to invoke our function with.
if [[ -z "$this_command" ]]; then
return
fi
# Invoke every function defined in our function array.
local preexec_function
local preexec_function_ret_value
local preexec_ret_value=0
for preexec_function in "${preexec_functions[@]:-}"; do
# Only execute each function if it actually exists.
# Test existence of function with: declare -[fF]
if type -t "$preexec_function" 1>/dev/null; then
__bp_set_ret_value "${__bp_last_ret_value:-}"
# Quote our function invocation to prevent issues with IFS
"$preexec_function" "$this_command"
preexec_function_ret_value="$?"
if [[ "$preexec_function_ret_value" != 0 ]]; then
preexec_ret_value="$preexec_function_ret_value"
fi
fi
done
# Restore the last argument of the last executed command, and set the return
# value of the DEBUG trap to be the return code of the last preexec function
# to return an error.
# If `extdebug` is enabled a non-zero return value from any preexec function
# will cause the user's command not to execute.
# Run `shopt -s extdebug` to enable
__bp_set_ret_value "$preexec_ret_value" "$__bp_last_argument_prev_command"
}
__bp_install() {
# Exit if we already have this installed.
if [[ "${PROMPT_COMMAND[*]:-}" == *"__bp_precmd_invoke_cmd"* ]]; then
return 1;
fi
trap '__bp_preexec_invoke_exec "$_"' DEBUG
# Preserve any prior DEBUG trap as a preexec function
local prior_trap
# we can't easily do this with variable expansion. Leaving as sed command.
# shellcheck disable=SC2001
prior_trap=$(sed "s/[^']*'\(.*\)'[^']*/\1/" <<<"${__bp_trap_string:-}")
unset __bp_trap_string
if [[ -n "$prior_trap" ]]; then
eval '__bp_original_debug_trap() {
'"$prior_trap"'
}'
preexec_functions+=(__bp_original_debug_trap)
fi
# Adjust our HISTCONTROL Variable if needed.
__bp_adjust_histcontrol
# Issue #25. Setting debug trap for subshells causes sessions to exit for
# backgrounded subshell commands (e.g. (pwd)& ). Believe this is a bug in Bash.
#
# Disabling this by default. It can be enabled by setting this variable.
if [[ -n "${__bp_enable_subshells:-}" ]]; then
# Set so debug trap will work be invoked in subshells.
set -o functrace > /dev/null 2>&1
shopt -s extdebug > /dev/null 2>&1
fi;
local existing_prompt_command
# Remove setting our trap install string and sanitize the existing prompt command string
existing_prompt_command="${PROMPT_COMMAND:-}"
# Edge case of appending to PROMPT_COMMAND
existing_prompt_command="${existing_prompt_command//$__bp_install_string/:}" # no-op
existing_prompt_command="${existing_prompt_command//$'\n':$'\n'/$'\n'}" # remove known-token only
existing_prompt_command="${existing_prompt_command//$'\n':;/$'\n'}" # remove known-token only
__bp_sanitize_string existing_prompt_command "$existing_prompt_command"
if [[ "${existing_prompt_command:-:}" == ":" ]]; then
existing_prompt_command=
fi
# Install our hooks in PROMPT_COMMAND to allow our trap to know when we've
# actually entered something.
PROMPT_COMMAND='__bp_precmd_invoke_cmd'
PROMPT_COMMAND+=${existing_prompt_command:+$'\n'$existing_prompt_command}
if (( BASH_VERSINFO[0] > 5 || (BASH_VERSINFO[0] == 5 && BASH_VERSINFO[1] >= 1) )); then
PROMPT_COMMAND+=('__bp_interactive_mode')
else
# shellcheck disable=SC2179 # PROMPT_COMMAND is not an array in bash <= 5.0
PROMPT_COMMAND+=$'\n__bp_interactive_mode'
fi
# Add two functions to our arrays for convenience
# of definition.
precmd_functions+=(precmd)
preexec_functions+=(preexec)
# Invoke our two functions manually that were added to $PROMPT_COMMAND
__bp_precmd_invoke_cmd
__bp_interactive_mode
}
# Sets an installation string as part of our PROMPT_COMMAND to install
# after our session has started. This allows bash-preexec to be included
# at any point in our bash profile.
__bp_install_after_session_init() {
# bash-preexec needs to modify these variables in order to work correctly
# if it can't, just stop the installation
__bp_require_not_readonly PROMPT_COMMAND HISTCONTROL HISTTIMEFORMAT || return
local sanitized_prompt_command
__bp_sanitize_string sanitized_prompt_command "${PROMPT_COMMAND:-}"
if [[ -n "$sanitized_prompt_command" ]]; then
# shellcheck disable=SC2178 # PROMPT_COMMAND is not an array in bash <= 5.0
PROMPT_COMMAND=${sanitized_prompt_command}$'\n'
fi;
# shellcheck disable=SC2179 # PROMPT_COMMAND is not an array in bash <= 5.0
PROMPT_COMMAND+=${__bp_install_string}
}
# Run our install so long as we're not delaying it.
if [[ -z "${__bp_delay_install:-}" ]]; then
__bp_install_after_session_init
fi;