/etc/bashrc_Apple_Terminal

bashrc_Apple_Terminal

# bash support for Terminal.


# Working Directory
#
# Tell the terminal about the current working directory at each prompt.

if [ -z "$INSIDE_EMACS" ]; then
    update_terminal_cwd() {
	# Identify the directory using a "file:" scheme URL, including
	# the host name to disambiguate local vs. remote paths.
	
	# Percent-encode the pathname.
	local url_path=''
	{
	    # Use LC_CTYPE=C to process text byte-by-byte. Ensure that
	    # LC_ALL isn't set, so it doesn't interfere.
	    local i ch hexch LC_CTYPE=C LC_ALL=
	    for ((i = 0; i < ${#PWD}; ++i)); do
		ch="${PWD:i:1}"
		if [[ "$ch" =~ [/._~A-Za-z0-9-] ]]; then
		    url_path+="$ch"
		else
		    printf -v hexch "%02X" "'$ch"
		    # printf treats values greater than 127 as
		    # negative and pads with "FF", so truncate.
		    url_path+="%${hexch: -2:2}"
		fi
	    done
	}
	
	printf '\e]7;%s\a' "file://$HOSTNAME$url_path"
    }
    PROMPT_COMMAND="update_terminal_cwd${PROMPT_COMMAND:+; $PROMPT_COMMAND}"
fi


# Resume Support: Save/Restore Shell State
#
# Terminal assigns each terminal session a unique identifier and
# communicates it via the TERM_SESSION_ID environment variable so that
# programs running in a terminal can save/restore application-specific
# state when quitting and restarting Terminal with Resume enabled.
#
# The following code defines a shell save/restore mechanism. Users can
# add custom state by defining a shell_session_save_user_state function
# that writes restoration commands to the session file at exit. e.g.,
# to save a variable:
#
#   shell_session_save_user_state() { echo MY_VAR="'$MY_VAR'" >> "$SHELL_SESSION_FILE"; }
#
# During shell startup the session file is executed. Old files are
# periodically deleted.
#
# The default behavior arranges to save and restore the bash command
# history independently for each restored terminal session. It also
# merges commands into the global history for new sessions. Because
# of this it is recommended that you set HISTSIZE and HISTFILESIZE to
# larger values.
#
# You may disable this behavior and share a single history by setting
# SHELL_SESSION_HISTORY to 0. There are some common user customizations
# that arrange to share new commands among running shells by
# manipulating the history at each prompt, and they typically include
# 'shopt -s histappend'; therefore, if the histappend shell option is
# enabled, per-session history is disabled by default. You may
# explicitly enable it by setting SHELL_SESSION_HISTORY to 1.
#
# The implementation of per-session command histories in combination
# with a shared global command history is incompatible with the
# HISTTIMEFORMAT variable--the timestamps are applied inconsistently
# to different parts of the history; therefore, if HISTTIMEFORMAT is
# defined, per-session history is disabled by default.
#
# Note that this uses PROMPT_COMMAND to enable per-session history
# the first time for each new session. If you customize PROMPT_COMMAND
# be sure to include the previous value. e.g.,
#
#   PROMPT_COMMAND="${PROMPT_COMMAND:+$PROMPT_COMMAND; }your_code_here"
#
# Otherwise, the per-session history won't take effect until the first
# restore.
#
# The save/restore mechanism is disabled if the following file exists:
#
#   ~/.bash_sessions_disable

if [ ${SHELL_SESSION_DID_INIT:-0} -eq 0 ] && [ -n "$TERM_SESSION_ID" ] && [ ! -e "$HOME/.bash_sessions_disable" ]; then
    
    # Do not perform this setup more than once (which shouldn't occur
    # unless the user's ~/.bash_profile executes /etc/profile, which
    # is normally redundant).
    SHELL_SESSION_DID_INIT=1
    
    # Set up the session directory/file.
    SHELL_SESSION_DIR="$HOME/.bash_sessions"
    SHELL_SESSION_FILE="$SHELL_SESSION_DIR/$TERM_SESSION_ID.session"
    mkdir -m 700 -p "$SHELL_SESSION_DIR"
    
    #
    # Restore previous session state.
    #
    
    if [ -r "$SHELL_SESSION_FILE" ]; then
	. "$SHELL_SESSION_FILE"
	rm "$SHELL_SESSION_FILE"
    fi
    
    #
    # Note: Use absolute paths to invoke commands in the exit code and
    # anything else that runs after user startup files, because the
    # search path may have been modified.
    #
    
    #
    # Arrange for per-session shell command history.
    #
    
    shell_session_history_allowed() {
	# Return whether per-session history should be enabled.
	if [ -n "$HISTFILE" ]; then
	    # If this defaults to off, leave it unset so that we can
	    # check again later. If it defaults to on, make it stick.
	    local allowed=0
	    if shopt -q histappend || [ -n "$HISTTIMEFORMAT" ]; then
		allowed=${SHELL_SESSION_HISTORY:-0}
	    else
		allowed=${SHELL_SESSION_HISTORY:=1}
	    fi
	    if [ $allowed -eq 1 ]; then
		return 0
	    fi
	fi
	return 1
    }
    
    if [ ${SHELL_SESSION_HISTORY:-1} -eq 1 ]; then
	SHELL_SESSION_HISTFILE="$SHELL_SESSION_DIR/$TERM_SESSION_ID.history"
	SHELL_SESSION_HISTFILE_NEW="$SHELL_SESSION_DIR/$TERM_SESSION_ID.historynew"
	SHELL_SESSION_HISTFILE_SHARED="$HISTFILE"
	
	shell_session_history_enable() {
	    (umask 077; /usr/bin/touch "$SHELL_SESSION_HISTFILE_NEW")
	    HISTFILE="$SHELL_SESSION_HISTFILE_NEW"
	    SHELL_SESSION_HISTORY=1
	}
	
	# If the session history already exists and isn't empty, start
	# using it now; otherwise, we'll use the shared history until
	# we've determined whether users have enabled/disabled this.
	if [ -s "$SHELL_SESSION_HISTFILE" ]; then
	    history -r "$SHELL_SESSION_HISTFILE"
	    shell_session_history_enable
	else
	    # At the first prompt, check whether per-session history should
	    # be enabled. Delaying until after user scripts have run allows
	    # users to opt in or out. If this doesn't get executed (because
	    # the user has replaced PROMPT_COMMAND instead of concatenating
	    # it), we'll check at shell exit; that works, but doesn't start
	    # the per-session history until the first restore.
	    
	    shell_session_history_check() {
		if [ ${SHELL_SESSION_DID_HISTORY_CHECK:-0} -eq 0 ]; then
		    SHELL_SESSION_DID_HISTORY_CHECK=1
		    if shell_session_history_allowed; then
			shell_session_history_enable
		    fi
		    # Remove this check if we can; otherwise, we rely on the
		    # variable above to prevent checking more than once.
		    if [ "$PROMPT_COMMAND" = "shell_session_history_check" ]; then
			unset PROMPT_COMMAND
		    elif [[ $PROMPT_COMMAND =~ (.*)(; *shell_session_history_check *| *shell_session_history_check *; *)(.*) ]]; then
			PROMPT_COMMAND="${BASH_REMATCH[1]}${BASH_REMATCH[3]}"
		    fi
		fi
	    }
	    PROMPT_COMMAND="shell_session_history_check${PROMPT_COMMAND:+; $PROMPT_COMMAND}"
	fi
	
	shell_session_save_history() {
	    # Save new history to an intermediate file so we can copy it.
	    shell_session_history_enable
	    history -a
	    # If the session history doesn't exist yet, copy the shared history.
	    if [ -f "$SHELL_SESSION_HISTFILE_SHARED" ] && [ ! -s "$SHELL_SESSION_HISTFILE" ]; then
		echo -ne '\n...copying shared history...'
		(umask 077; /bin/cp "$SHELL_SESSION_HISTFILE_SHARED" "$SHELL_SESSION_HISTFILE")
	    fi
	    # Save new history to the per-session and shared files.
	    echo -ne '\n...saving history...'
	    (umask 077; /bin/cat "$SHELL_SESSION_HISTFILE_NEW" >> "$SHELL_SESSION_HISTFILE_SHARED")
	    (umask 077; /bin/cat "$SHELL_SESSION_HISTFILE_NEW" >> "$SHELL_SESSION_HISTFILE")
	    : >| "$SHELL_SESSION_HISTFILE_NEW"
	    # If there is a history file size limit, apply it to the files.
	    if [ -n "$HISTFILESIZE" ]; then
		echo -n 'truncating history files...'
		HISTFILE="$SHELL_SESSION_HISTFILE_SHARED"
		HISTFILESIZE="$HISTFILESIZE"
		HISTFILE="$SHELL_SESSION_HISTFILE"
		HISTFILESIZE="$size"
		HISTFILE="$SHELL_SESSION_HISTFILE_NEW"
	    fi
	    echo -ne '\n...'
	}
    fi
    
    #
    # Arrange to save session state when exiting the shell.
    #
    
    shell_session_save() {
	# Save the current state.
	if [ -n "$SHELL_SESSION_FILE" ]; then
	    echo -n 'Saving session...'
	    (umask 077; echo 'echo Restored session: "$(/bin/date -r '$(/bin/date +%s)')"' >| "$SHELL_SESSION_FILE")
	    declare -F shell_session_save_user_state >/dev/null && shell_session_save_user_state
	    shell_session_history_allowed && shell_session_save_history
	    echo 'completed.'
	fi
    }
    
    # Delete old session files. (Not more than once a day.)
    SHELL_SESSION_TIMESTAMP_FILE="$SHELL_SESSION_DIR/_expiration_check_timestamp"
    shell_session_delete_expired() {
	if ([ ! -e "$SHELL_SESSION_TIMESTAMP_FILE" ] || [ -z "$(/usr/bin/find "$SHELL_SESSION_TIMESTAMP_FILE" -mtime -1d)" ]); then
	    local expiration_lock_file="$SHELL_SESSION_DIR/_expiration_lockfile"
	    if /usr/bin/shlock -f "$expiration_lock_file" -p $$; then
		echo -n 'Deleting expired sessions...'
		local delete_count=$(/usr/bin/find "$SHELL_SESSION_DIR" -type f -mtime +2w -print -delete | /usr/bin/wc -l)
		[ "$delete_count" -gt 0 ] && echo $delete_count' completed.' || echo 'none found.'
		(umask 077; /usr/bin/touch "$SHELL_SESSION_TIMESTAMP_FILE")
		/bin/rm "$expiration_lock_file"
	    fi
	fi
    }
    
    # Update saved session state when exiting.
    shell_session_update() {
	shell_session_save && shell_session_delete_expired
    }
    trap shell_session_update EXIT
fi

I'm determined to set up bash as my default shell on macOS Ventura. I've read some negative things about the default (Apple-supplied) version of /etc/bashrc_Apple_Terminal... and then I ran across your Gist in my search. But it has no explanation to go along with it. Can you provide a few words that explain how it's different from the default, and some motivation for its use??