Added bash functions preexec() and precmd()

diff --git a/lib/preexec.bash b/lib/preexec.bash
new file mode 100644 (file)
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--- /dev/null
+++ b/lib/preexec.bash
@@ -0,0 +1,195 @@
+#!/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
+}