lib/history: new functions _bash_it_history_auto_*()

Two new functions `_bash_it_history_auto_save()` and `_bash_it_history_auto_load()`, which append new history to disk and load new history from disk, respectively.

See #1595 for discussion.

Author: gaelicWizard

clean_files.txt

@@ -77,6 +77,7 @@ completion/available/vuejs.completion.bash
 completion/available/wpscan.completion.bash
 
 # libraries
+lib/history.bash
 lib/utilities.bash
 
 # plugins

lib/history.bash

@@ -0,0 +1,49 @@
+# shellcheck shell=bash
+#
+# Functions for working with Bash's command history.
+
+function _bash_it_history_auto_init() {
+	safe_append_preexec '_bash_it_history_auto_save'
+	safe_append_prompt_command '_bash_it_history_auto_load'
+}
+
+function _bash_it_history_auto_save() {
+	case $HISTCONTROL in
+		*'noauto'* | *'autoload'*)
+			: # Do nothing, as configured.
+			;;
+		*'auto'*)
+			# Append new history from this session to the $HISTFILE
+			history -a
+			;;
+		*)
+			# Append *only* if shell option `histappend` has been enabled.
+			shopt -q histappend && history -a && return
+			;;
+	esac
+}
+
+function _bash_it_history_auto_load() {
+	case $HISTCONTROL in
+		*'noauto'*)
+			: # Do nothing, as configured.
+			;;
+		*'autosave'*)
+			# Append new history from this session to the $HISTFILE
+			history -a
+			;;
+		*'autoloadnew'*)
+			# Read new entries from $HISTFILE
+			history -n
+			;;
+		*'auto'*)
+			# Blank in-memory history, then read entire $HISTFILE fresh from disk.
+			history -a && history -c && history -r
+			;;
+		*)
+			: # Do nothing, default.
+			;;
+	esac
+}
+
+_bash_it_history_auto_init

plugins/available/history.plugin.bash

@@ -5,15 +5,14 @@ about-plugin 'improve history handling with sane defaults'
 # variable when the shell exits, rather than overwriting the file.
 shopt -s histappend
 
-# erase duplicates; alternative option: HISTCONTROL=ignoredups
-: "${HISTCONTROL:=ignorespace:erasedups}"
+# 'ignorespace': don't save command lines which begin with a space to history
+# 'erasedups' (alternative 'ignoredups'): don't save duplicates to history
+# 'autoshare': automatically share history between multiple running shells
+: "${HISTCONTROL:=ignorespace:erasedups:autoshare}"
 
 # resize history to 100x the default (500)
 : "${HISTSIZE:=50000}"
 
-# Flush history to disk after each command.
-export PROMPT_COMMAND="history -a;${PROMPT_COMMAND}"
-
 function top-history() {
 	about 'print the name and count of the most commonly run tools'
 

themes/base.theme.bash

@@ -620,6 +620,6 @@ function safe_append_prompt_command {
 }
 
 function _save-and-reload-history() {
-	local autosave=${1:-0}
-	[[ $autosave -eq 1 ]] && history -a && history -c && history -r
+	[[ ${1:-${autosave:-${HISTORY_AUTOSAVE:-0}}} -eq 1 ]] && local HISTCONTROL="${HISTCONTROL:-}${HISTCONTROL:+:}autoshare"
+	_bash_it_history_auto_save && _bash_it_history_auto_load
 }