lec6vid2Functions-Backup

#!/bin/bash

log() {                            # you can also use: function log { }
   local MESSAGE=${@}  # local shell builtins make the variable local and scope to the function, so that it can be accessed only inside the function
   echo "You called the log function ${MESSAGE}"
}

log 'HELLO'
log 'this is fun'

# this function send messages to syslog and to standard output if verbose is true 
log_2(){
    local VERBOSE=$1
    shift
    local MESSAGE=${@}
    if [ $VERBOSE = 'true' ]
    then 
       echo $MESSAGE
    fi   
    logger -t lec6vid2Functions ${MESSAGE} # logger - enter messages into the system log
}

readonly VERBOSITY='true'     # readonly means constant variable 
log_2 $VERBOSITY 'DEBNAKAN MITRA' 

#--------------------------
# Function to create a backup of a file ,  returns a non zero status on error
backup(){
    FILE=${1}
    # make sure file exists
    if [ -a "${FILE}" ]   # -a file True if file exists.
    then
       local BACKUP_FILE="/var/tmp/$(basename ${FILE}).$(date +%F%N)" # %F -- full date; like %+4Y-%m-%d , basename -- name of the file without the full path
       log "BACKING UP $FILE TO $BACKUP_FILE"
       cp -p $FILE $BACKUP_FILE     #  -p  same as --preserve=mode,ownership,timestamps
    else
       # if file doesnot exist , return a non zero exit status
       return 1
    fi      
}

backup '/home/devfedora/telegram_files/Q1.pdf'