$ printf "You can use \n newline like this"
You can use
 newline like this

bash-4.3$ printf "no-newline"
no-newlinebash-4.3$

ps | grep " 3 $FD " | grep -v grep >/dev/null
      if [ "$?" -eq "0" ]; then

#!/sbin/sh

OUTFD=$2
ZIP=$3
MISC=/tmp/misc
SOURCE_P=$MISC/system/priv-app
DEST_P=/system/priv-app

mkdir $MISC
mkdir $SOURCE_P


if readlink /proc/$$/fd/"$OUTFD" 2>/dev/null | grep -q "/tmp" ; then
  # rerouted to log file, we don't want our ui_print commands going there
  OUTFD=0

  # we are probably running in embedded mode, see if we can find the right fd
  # we know the fd is a pipe and that the parent updater may have been started as
  # 'update-binary 3 fd zipfile'
  for FD in /proc/$$/fd/*; do

backup() {
  ui_print "Backing up $1"
  cp /system/priv-app/"$1"/"$1".apk /data/media/0/Documents/LGAppBak/"$1".apk
}

install_app() {
  ui_print "Installing $1"
  cp $SOURCE_P/"$1"/"$1".apk $DEST_P/"$1"/"$1".apk
  chmod 0644 $DEST_P/"$1"/"$1".apk
}

backup "LGSystemUI"

backup "LGQuickTools"

backup "LGSettings"

backup "LGSignBoard"

    #!/bin/bash
    ui_print(){
        if [ -n "$1"  ];
        then
            printf "ui_print $1\nui_print\n"     >> /proc/self/fd/$OUTFD
        else
            # classical way of reading stuff in shell
            # this defaults to stdin
            while IFS=  read -r line
            do
                printf "ui_print $line\nui_print\n" >> /proc/self/fd/$OUTFD
            done
            # this stuff is to ensure
            [ -n "$line" ] && echo "$line"
        fi
    }

 printf "ui_print $1\nui_print\n"     >> /proc/self/fd/$OUTFD
           ^-- SC2059: Don't use variables in the printf format string. Use printf "..%s.." "$foo".

 if readlink /proc/$$/fd/"$FD" 2>/dev/null | grep -q "pipe" ; then
        if pgrep -f "3 $FD" ; then
        OUTFD=$FD
        break
      fi
    fi
  done

for FD in /proc/$$/fd/*; do