Shell Programming and Scripting

# Read file cred.txt (with one IP per line), connect to servers (one at a time), and download directory listing
i=1
param=$(sed -n "{$1}p" $parm_dir/cdm_param.txt) #Get the last saved parameter in cdm_param.txt (Date in format YYYYMMDD when the script was last successfully run)
param=$(date -d $param+%Y-%m) # Convert YYYYMMDD to YYYY-DD
while read line; do
	host=$line
	ssh $user@$host ls -1 $was7sourcedir/$src_file_name$param'*' > $workdir/ftpList$i.txt
	awk -F '{print substr($line,length($line)-14,10)}' ftpList$i.txt > Dates$i.txt #Save the date part of each file name
															  #in the directory listing downloaded previously.
	awk -F '{print substr($line,length($line)-31,27)}' $workdir/ftpList$i.txt > $workdir/Files$i.txt	#Save the name of each file.
		linenum=0 #Auxiliary variable for sed. Will be used to match the line where the condition is satisfied with the corresponding file.
		
		while read list; do
		linenum=$((linenum+1))
		date_of_file=$(date -d "$list" +%Y%m%d) #Convert the modification datetime of each file to format YYYYMMDD
		    if [ "$date_of_file" -gt "$param" ] ; then #Compare with the last saved parameter
			file=$(sed -n "${linenum}p" $workdir/Files$i.txt)	#If the condition is satisfied, use sed to get the name of the file
														#in the same line of Files$i.txt.
		while read line2; do	#Connect again and download file when the above condition has been satisfied.
			sftp $user@$host <<END_RETRIEVE
			cd $was7sourcedir
			get $file
			quit
END_RETRIEVE

awk -F '{print substr($line,length($line)-14,10)}' ftpList$i.txt > Dates$i.txt #Save the date part of each file name
															  #in the directory listing downloaded previously.
	awk -F '{print substr($line,length($line)-31,27)}' $workdir/ftpList$i.txt > $workdir/Files$i.txt	#Save the name of each file.
		linenum=0 #Auxiliary variable for sed. Will be used to match the line where the condition is satisfied with the corresponding file.

awk -F '{print substr($line,length('$line')-14,10)}' ftpList$i.txt > Dates$i.txt

awk -F '{print substr('$line',length('$line')-14,10)}' ftpList$i.txt > Dates$i.txt