#!/bin/bash

askfirst () {
#- Asks the user if they would like to perform the command given as
#parameters or on stdin (call with sole paremeter of "-").
#- Return code is the return code of the command,
#127 if no command or 126 if user chooses to not run the command.
#- All user IO is done on stderr; something like:
#  askfirst ls -al "2>&1" | tee -a /tmp/teefile
#allows you to log all output from the command.
#- Set ASKFIRSTHELP to some hint as to why you're asking the user to
#run this.  No problem if left blank.  It should be the answer to the
#question, "Why do you want me to run this?"
#- If your sudo command is something other than "sudo", set
#SUDO="/path/to/sudo"
#- askfirst can be used in any step of a pipeline.  It can even
#be used in multiple steps, but the user prompts get mixed together.

    unset DOTHIS
    if [ $# -eq 0 ]; then
	echo 'askfirst invoked without any parameters; use at least "-" to read ' >/dev/stderr
	echo 'command from stdin.' >/dev/stderr
    else
	if [ "z$*" = 'z-' ]; then	#command given on stdin - we hope ;-)
	    read DOTHIS
	else
	    DOTHIS="$*"
	fi
    fi
    if [ -z "$DOTHIS" ]; then
	return 127
    fi

    SUDO=${SUDO:-"sudo"}
    AVAILABLEOPTIONS="(Y/N/"
    SUDOHELP=""
    if [ "$EUID" != "0" ]; then	#Little point in asking root if they want to use sudo.
	#Cannot put quotes around "sudo *"; use backslash escape instead
	case "$DOTHIS" in	#No point in asking for sudo if sudo already there.
	$SUDO\ *|/usr/bin/sudo\ *)
	    :								;;
	*)
	    AVAILABLEOPTIONS="${AVAILABLEOPTIONS}S/"
	    SUDOHELP="S\tRun the command under sudo"			;;
	esac
    fi
    AVAILABLEOPTIONS="${AVAILABLEOPTIONS}E/?)"

    unset FINISHED
    while [ "$FINISHED" != "YES" ]; do
	echo "  Shall I run \"$DOTHIS\"" >/dev/stderr
	echo -n "  as $USER in `pwd` ${AVAILABLEOPTIONS}:" >/dev/stderr
	unset CHOICE
	#Reading from stderr falls in the "decidedly cheesy" category and would probably
	#give the POSIX group heart murmurs, but it does work on Linux and frees up stdin
	#for feeding in the command to run.
	read CHOICE </dev/stderr
	case "$CHOICE" in
	Y|y)
	    eval "$DOTHIS"
	    AFRETVAL="$?"
	    FINISHED="YES"						;;
	N|n)
	    echo "  NOT running \"$DOTHIS\"" >/dev/stderr
	    AFRETVAL=126	#False; command failed, in a sense.
	    FINISHED="YES"						;;
	S|s)
	    eval "$SUDO $DOTHIS"
	    AFRETVAL="$?"
	    FINISHED="YES"						;;
	E|e)
	    echo "  NOT running \"$DOTHIS\", exiting" >/dev/stderr
	    exit 1							;;    
	?)
	    echo "  " >/dev/stderr
	    if [ -n "$ASKFIRSTHELP" ]; then
		echo "  Here is why you're being asked to run this:" >/dev/stderr
		echo "  $ASKFIRSTHELP" >/dev/stderr
	    fi
	    echo "  Here are your options:" >/dev/stderr
	    echo -e "  Y\tYes, run the command" >/dev/stderr
	    echo -e "  N\tNo, do not run the command" >/dev/stderr
	    if [ -n "$SUDOHELP" ]; then
		echo -e "  $SUDOHELP" >/dev/stderr
	    fi
	    echo -e "  E\tExit the program completely and don't run the command" >/dev/stderr
	    echo -e "  ?\tShow this help" >/dev/stderr			;;
	*)
	    echo "  Unrecognized choice." >/dev/stderr			;;
	esac
    done
    return $AFRETVAL
}


#Working examples
#Simple commands
ASKFIRSTHELP="Give a directory listing." askfirst ls -al
ASKFIRSTHELP="Creating a flag file for later test." askfirst touch /tmp/asdf

#Sudo already in command
ASKFIRSTHELP="sudo in command" askfirst sudo touch /tmp/asdf
ASKFIRSTHELP="/usr/bin/sudo in command" askfirst /usr/bin/sudo touch /tmp/asdf

#Give command to run on stdin instead of on the command line.
echo "ls -al" | ASKFIRSTHELP="Piped in command" askfirst -

#Assigning output to a string
OUTTEXT=`ASKFIRSTHELP='Help line' askfirst 'ls -al /root'`
echo separator
echo "$OUTTEXT" | head

#Pipe stdout and stderr into tee
ASKFIRSTHELP="Dir listing of root" askfirst "ls -al /root 2>&1" | tee -a /tmp/teefile
#Alternate form, works just as well
ASKFIRSTHELP="Dir listing of root" askfirst ls -al /root "2>&1" | tee -a /tmp/teefile

#In second stage of 3 stage pipeline
echo Hi | ASKFIRSTHELP="Pass along welcome string as root." askfirst cat | cat

#By setting PRECOMMAND to one of the following, you can run raw, run
#under sudo, or use askfirst to let user choose.  The eval's in 1+2 are
#necessary because of possible quoting of command parmaters like "2>&1".
PRECOMMAND="eval"
#PRECOMMAND="eval sudo"
#PRECOMMAND="askfirst"

ASKFIRSTHELP="I need to see if root's home directory exists." $PRECOMMAND ls -al /root "2>&1" | sed -e 's/^/ZZZ/'