CSC Ansible Playbooks
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# -- Bash support for ZSH-like 'preexec' and 'precmd' functions.
# '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 (
# Forked from Original Author: Glyph Lefkowitz
# V0.3.1
# 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. If you have anything that's using the Debug Trap, change it to use
# preexec. (Optional) change anything using PROMPT_COMMAND to now use
# precmd instead.
# Note: This module requires two bash features which you must not otherwise be
# using: the "DEBUG" trap, and the "PROMPT_COMMAND" variable. prexec_and_precmd_install
# will override these and if you override one or the other this will most likely break.
# Avoid duplicate inclusion
if [[ "$__bp_imported" == "defined" ]]; then
return 0
# Should be available to each precmd and preexec
# functions, should they want it.
# Command to set our preexec trap. It's invoked once via
# PROMPT_COMMAND and then removed.
__bp_trap_install_string="trap '__bp_preexec_invoke_exec' DEBUG;"
# Remove ignorespace and or replace ignoreboth from HISTCONTROL
# so we can accurately invoke preexec with a command from our
# history even if it starts with a space.
__bp_adjust_histcontrol() {
local histcontrol
# Replace ignoreboth with ignoredups
if [[ "$histcontrol" == *"ignoreboth"* ]]; then
export HISTCONTROL="$histcontrol"
# This variable describes whether we are currently in "interactive mode";
# i.e. whether this shell has just executed a prompt and is waiting for user
# input. It documents whether the current command invoked by the trace hook is
# run interactively by the user; it's set immediately after the prompt hook,
# and unset as soon as the trace hook is run.
__bp_trim_whitespace() {
local var=$@
var="${var#"${var%%[![:space:]]*}"}" # remove leading whitespace characters
var="${var%"${var##*[![:space:]]}"}" # remove trailing whitespace characters
echo -n "$var"
# This function is installed as part of the PROMPT_COMMAND;
# It sets a variable to indicate that the prompt was just displayed,
# to allow the DEBUG trap to know that the next command is likely interactive.
__bp_interactive_mode() {
# This function is installed as part of the PROMPT_COMMAND.
# It will invoke any functions defined in the precmd_functions array.
__bp_precmd_invoke_cmd() {
# Save the returned value from our last command
# For every function defined in our function array. Invoke it.
local precmd_function
for precmd_function in "${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
# 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 $1
__bp_in_prompt_command() {
local prompt_command_array
IFS=';' read -ra prompt_command_array <<< "$PROMPT_COMMAND"
local trimmed_arg
trimmed_arg=$(__bp_trim_whitespace "$1")
local command
for command in "${prompt_command_array[@]}"; do
local trimmed_command
trimmed_command=$(__bp_trim_whitespace "$command")
# Only execute each function if it actually exists.
if [[ "$trimmed_command" == "$trimmed_arg" ]]; then
return 0
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() {
# 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 "$__bp_delay_install" ]]; then
if [[ -n "$COMP_LINE" ]]; then
# We're in the middle of a completer. This obviously can't be
# an interactively issued command.
if [[ -z "$__bp_preexec_interactive_mode" ]]; then
# We're doing something related to displaying the prompt. Let the
# prompt set the title instead of me.
# If we're in a subshell, then the prompt won't be re-displayed to put
# us back into interactive mode, so let's not set the variable back.
# In other words, if you have a subshell like
# (sleep 1; sleep 2)
# You want to see the 'sleep 2' as a set_command_title as well.
if [[ 0 -eq "$BASH_SUBSHELL" ]]; then
if __bp_in_prompt_command "$BASH_COMMAND"; then
# If we're executing something inside our prompt_command then we don't
# want to call preexec. Bash prior to 3.1 can't detect this at all :/
local this_command
this_command=$(HISTTIMEFORMAT= history 1 | { read -r _ this_command; echo "$this_command"; })
# Sanity check to make sure we have something to invoke our function with.
if [[ -z "$this_command" ]]; then
# If none of the previous checks have returned out of this function, then
# the command is in fact interactive and we should invoke the user's
# preexec functions.
# For every function defined in our function array. Invoke it.
local preexec_function
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
$preexec_function "$this_command"
# Returns PROMPT_COMMAND with a semicolon appended
# if it doesn't already have one.
__bp_prompt_command_with_semi_colon() {
# Trim our existing PROMPT_COMMAND
local trimmed
trimmed=$(__bp_trim_whitespace "$PROMPT_COMMAND")
# Take our existing prompt command and append a semicolon to it
# if it doesn't already have one.
local existing_prompt_command
if [[ -n "$trimmed" ]]; then
echo -n "$existing_prompt_command"
__bp_install() {
# Remove setting our trap from PROMPT_COMMAND
# Remove this function from our PROMPT_COMMAND
# Exit if we already have this installed.
if [[ "$PROMPT_COMMAND" == *"__bp_precmd_invoke_cmd"* ]]; then
return 1;
# Adjust our HISTCONTROL Variable if needed.
# Issue #25. Setting debug trap for subshells causes sessions to exit for
# backgrounded subshell commands (e.g. (pwd)& ). Believe this is a bug in Bash.
# Disabling this by default. It can be enabled by setting this variable.
if [[ -n "$__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
local existing_prompt_command
# Install our hooks in PROMPT_COMMAND to allow our trap to know when we've
# actually entered something.
PROMPT_COMMAND="__bp_precmd_invoke_cmd; ${existing_prompt_command} __bp_interactive_mode;"
trap '__bp_preexec_invoke_exec' DEBUG;
# Add two functions to our arrays for convenience
# of definition.
# Since this is in PROMPT_COMMAND, invoke any precmd functions we have defined.
# Put us in interactive mode for our first command.
# Sets our trap and __bp_install as part of our PROMPT_COMMAND to install
# after our session has started. This allows bash-preexec to be inlucded
# at any point in our bash profile. Ideally we could set our trap inside
# __bp_install, but if a trap already exists it'll only set locally to
# the function.
__bp_install_after_session_init() {
# Make sure this is bash that's running this and return otherwise.
if [[ -z "$BASH_VERSION" ]]; then
return 1;
local existing_prompt_command
# Add our installation to be done last via our PROMPT_COMMAND. These are
# removed by __bp_install when it's invoked so it only runs once.
PROMPT_COMMAND="${existing_prompt_command} $__bp_trap_install_string __bp_install;"
# Run our install so long as we're not delaying it.
if [[ -z "$__bp_delay_install" ]]; then