lec8vid3project

#!/bin/bash

# a list of servers one per line
SERVER_LIST='/home/devfedora/Debankan/bash-scripting/lec8vid3.txt'

# options for the ssh command 
SSH_OPTIONS='-o connectTimeout=2'

usage(){
   echo "usage: ${0} [-nsv] [-f file] COMMAND " >&2
   echo 'Executes COMMANDS as a single command on every server.' >&2
   echo " -f FILE   use FILE for the list of severs .Default ${SERVER_LIST}" >&2
   echo ' -n        Dry run mode.Display the COMMAND that would have been executed and exit ' >&2
   echo ' -s        Execute command using sudo on the remote server' >&2
   echo ' -v        verbose mode , display server name using executing command' >&2
   exit 1  
}

# Make sure the script does not begin with Superuser privilages 
if [ "${UID}" -eq 0 ]
then 
   echo 'Do not execute the script as roo.Use -s instead ' >&2
   exit 1
fi

# Parse the options 
while getopts f:nsv OPTION
do
   case ${OPTION} in
   f) SERVER_LIST="${OPTARG}" ;;
   n) DRY_RUN='true' ;;
   v) VERBOSE='true' ;;
   s) SUDO='sudo' ;;
   ?) usage ;;
   esac
done       

#Remove the options while leaving thew remaining arguments 
shift "$(( OPTIND -1 ))" # NOT ABLE TO UNDERSTAND WHY WOULD WE USE THIS COMMAND , WHATS THE FUNCTION BEHIND IT
                         # >>> NOW I UNDERSTOOD THIS LINE REMOVE EVERYTHING BEFORE COMMAND AND GIVE NEXT LINE EVRYTHING LEFT AS COMMAND TO ${@}

# Anything that remains on the command line is treated as command
COMMENT="${@}"

# If the user doesn't supply atleast one argument give them help 
if [ "${#}" -lt 1 ]
then 
   usage
   exit 1
fi    

# Make sure the server file exists 
if [ ! -e "${SERVER_LIST}" ]
then
  echo "Server file doesn't exist" >&2
  exit 1
fi

# expect the best , prepare for the worst
EXIT_STATUS='0'

#Loop through the server list 
for SERVER in $(cat ${SERVER_LIST})  
do 
  # check verbose 
  if [[ "${VERBOSE}" -eq 'true' ]]
  then 
     echo "${SERVER}"
  fi
  
  SSH_COMMAND="ssh ${SSH_OPTIONS} ${SERVER} ${SUDO} ${COMMAND}"
  
  if [[ "${DRY_RUN}" -eq 'true' ]]
  then
     echo "dry run: ${SSH_COMMAND}"  
  else
     ${SSH_COMMAND}
     SSH_EXIT_STATUS="${?}"
     
     # Capture if any non-zer exit status from ${SSH_COMMAND} and report it to the user  
     if [ $SSH_EXIT_STATUS -ne 0 ]
      then 
         echo "Execution of ${SERVER} failed" >&2
         # we are not writing any exit status because , if one server fail we want to continue the script with other servers
     fi
  fi
done

exit $SSH_EXIT_STATUS