Shell Programming and Scripting

#!/bin/bash

# Login credentials
user='ftp-user-name' #Do not forget to enclose inside single or double quotes
pass='ftp-password'
directory='/absolute/path/to/remote/ftp/directory/'
host='IP Address or hostname of remote host'

# Set time
# perl -e 'print time' will return the current time in Unix epoch format
# So if you substract 43200, that should give you the current time minus 30 minutes in Unix epoch format:
time=$(perl -e 'print time-43200')

# Connect to host and download the listing of the remote directory
ftp -n $host <<END_GET_LIST
	quote USER $user
	quote PASS $pass
	cd $directory
	ls -l ftpList.txt
	quit
END_GET_LIST
# Disconnect from remote host

# Save the 6th, 7th, and 8th field of the directory listing (i.e. Aug 15 5:15) of each line into file Dates.txt
awk -F ' ' '{print $6,$7,$8}' ftpList.txt > 'Dates.txt'

# Save the 9th field of the directory listing (file name) of each line into file Files.txt
awk -F ' ' '{print $9}' ftpList.txt > 'Files.txt'

linenum=0 #Auxiliary variable for sed.

while read list; do
	linenum=$((linenum+1))
	#Convert the modification datetime of each file to Unix's epoch
	epoch=$(perl -MFile::stat -e "print stat('$list')->mtime")
	if [ $epoch -gt $time ] ; then
		file=$(sed -n "${linenum}p" Files.txt)	#If the condition is satisfied, use sed to get the name of the file
												#in the same line of Files.txt.
#Connect again and download file when the condition above has been satisfied.
		ftp -n $host <<END_RETRIEVE
			quote USER $user
			quote PASS $pass
			cd $directory
			get $file
			quit
END_RETRIEVE
	fi
done < 'Dates.txt'

perl -MFile::stat -e "print stat('$list')->mtime"

perl -MFile::stat -e "print stat('yourfile')->mtime"