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#!/bin/bash
# http://www.twistedmatrix.com/users/glyph/preexec.bash.txt
# preexec.bash -- Bash support for ZSH-like 'preexec' and 'precmd' functions.
# The 'preexec' function is executed before each interactive command is
# executed, with the interactive command as its argument. The 'precmd'
# function is executed before each prompt is displayed.
# To use, in order:
# 1. source this file
# 2. define 'preexec' and/or 'precmd' functions (AFTER sourcing this file),
# 3. as near as possible to the end of your shell setup, run 'preexec_install'
# to kick everything off.
# Note: this module requires 2 bash features which you must not otherwise be
# using: the "DEBUG" trap, and the "PROMPT_COMMAND" variable. preexec_install
# will override these and if you override one or the other this _will_ break.
# This is known to support bash3, as well as *mostly* support bash2.05b. It
# has been tested with the default shells on MacOS X 10.4 "Tiger", Ubuntu 5.10
# "Breezy Badger", Ubuntu 6.06 "Dapper Drake", and Ubuntu 6.10 "Edgy Eft".
# Copy screen-run variables from the remote host, if they're available.
if [[ "$SCREEN_RUN_HOST" == "" ]]
then
SCREEN_RUN_HOST="$LC_SCREEN_RUN_HOST"
SCREEN_RUN_USER="$LC_SCREEN_RUN_USER"
fi
# This variable describes whether we are currently in "interactive mode";
# i.e. whether this shell has just executed a prompt and is waiting for user
# input. It documents whether the current command invoked by the trace hook is
# run interactively by the user; it's set immediately after the prompt hook,
# and unset as soon as the trace hook is run.
preexec_interactive_mode=""
# Default do-nothing implementation of preexec.
function preexec () {
true
}
# Default do-nothing implementation of precmd.
function precmd () {
true
}
# This function is installed as the PROMPT_COMMAND; it is invoked before each
# interactive prompt display. It sets a variable to indicate that the prompt
# was just displayed, to allow the DEBUG trap, below, to know that the next
# command is likely interactive.
function preexec_invoke_cmd () {
precmd
preexec_interactive_mode="yes"
}
# This function is installed as the DEBUG trap. It is invoked before each
# interactive prompt display. Its purpose is to inspect the current
# environment to attempt to detect if the current command is being invoked
# interactively, and invoke 'preexec' if so.
function preexec_invoke_exec () {
if [[ -n "$COMP_LINE" ]]
then
# We're in the middle of a completer. This obviously can't be
# an interactively issued command.
return
fi
if [[ -z "$preexec_interactive_mode" ]]
then
# We're doing something related to displaying the prompt. Let the
# prompt set the title instead of me.
return
else
# If we're in a subshell, then the prompt won't be re-displayed to put
# us back into interactive mode, so let's not set the variable back.
# In other words, if you have a subshell like
# (sleep 1; sleep 2)
# You want to see the 'sleep 2' as a set_command_title as well.
if [[ 0 -eq "$BASH_SUBSHELL" ]]
then
preexec_interactive_mode=""
fi
fi
if [[ "preexec_invoke_cmd" == "$BASH_COMMAND" ]]
then
# Sadly, there's no cleaner way to detect two prompts being displayed
# one after another. This makes it important that PROMPT_COMMAND
# remain set _exactly_ as below in preexec_install. Let's switch back
# out of interactive mode and not trace any of the commands run in
# precmd.
# Given their buggy interaction between BASH_COMMAND and debug traps,
# versions of bash prior to 3.1 can't detect this at all.
preexec_interactive_mode=""
return
fi
# In more recent versions of bash, this could be set via the "BASH_COMMAND"
# variable, but using history here is better in some ways: for example, "ps
# auxf | less" will show up with both sides of the pipe if we use history,
# but only as "ps auxf" if not.
local this_command=`history 1 | sed -e "s/^[ ]*[0-9]*[ ]*//g"`;
# If none of the previous checks have earlied out of this function, then
# the command is in fact interactive and we should invoke the user's
# preexec hook with the running command as an argument.
preexec "$this_command"
}
# Execute this to set up preexec and precmd execution.
function preexec_install () {
# *BOTH* of these options need to be set for the DEBUG trap to be invoked
# in ( ) subshells. This smells like a bug in bash to me. The null stderr
# redirections are to quiet errors on bash2.05 (i.e. OSX's default shell)
# where the options can't be set, and it's impossible to inherit the trap
# into subshells.
set -o functrace > /dev/null 2>&1
shopt -s extdebug > /dev/null 2>&1
# Finally, install the actual traps.
PROMPT_COMMAND="${PROMPT_COMMAND};preexec_invoke_cmd"
trap 'preexec_invoke_exec' DEBUG
}
# Since this is the reason that 99% of everybody is going to bother with a
# pre-exec hook anyway, we'll include it in this module.
# Change the title of the xterm.
function preexec_xterm_title () {
local title="$1"
echo -ne "\033]0;$title\007" > /dev/stderr
}
function preexec_screen_title () {
local title="$1"
echo -ne "\033k$1\033\\" > /dev/stderr
}
# Abbreviate the "user@host" string as much as possible to preserve space in
# screen titles. Elide the host if the host is the same, elide the user if the
# user is the same.
function preexec_screen_user_at_host () {
local RESULT=""
if [[ "$SCREEN_RUN_HOST" == "$SCREEN_HOST" ]]
then
return
else
if [[ "$SCREEN_RUN_USER" == "$USER" ]]
then
echo -n "@${SCREEN_HOST}"
else
echo -n "${USER}@${SCREEN_HOST}"
fi
fi
}
function preexec_xterm_title_install () {
# These functions are defined here because they only make sense with the
# preexec_install below.
function precmd () {
preexec_xterm_title "${TERM} - ${USER}@${SCREEN_HOST} `dirs -0` $PROMPTCHAR"
if [[ "${TERM}" == screen ]]
then
preexec_screen_title "`preexec_screen_user_at_host`${PROMPTCHAR}"
fi
}
function preexec () {
preexec_xterm_title "${TERM} - $1 {`dirs -0`} (${USER}@${SCREEN_HOST})"
if [[ "${TERM}" == screen ]]
then
local cutit="$1"
local cmdtitle=`echo "$cutit" | cut -d " " -f 1`
if [[ "$cmdtitle" == "exec" ]]
then
local cmdtitle=`echo "$cutit" | cut -d " " -f 2`
fi
if [[ "$cmdtitle" == "screen" ]]
then
# Since stacked screens are quite common, it would be nice to
# just display them as '$$'.
local cmdtitle="${PROMPTCHAR}"
else
local cmdtitle=":$cmdtitle"
fi
preexec_screen_title "`preexec_screen_user_at_host`${PROMPTCHAR}$cmdtitle"
fi
}
preexec_install
}
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