Litle Bit of Shell Script - Part 2

I Just made a change in the script. Actually, the script was working just fine but I had only one single problem with it. If I had two file on the directory to be compressed, the script would make only one compressed file. Although this situation might not happen in the environment I'd like to implement this script, I was not comfortable with it. Tried many ways to overcome this problem but, in fact, the original script with only one change was able to give me the result I wanted.
The original script was:

NOW=$(date +"%m-%d-%Y")
FILE="Prime-Backup.$NOW.tar.gz.$$"
tar  -zcf  $FILE  $files

Then a change to :

NOW=$(date +"%m-%d-%Y")
    tar -cz -f "$file".$NOW.MyFile.tar.gz  "$file"

I Keep the variable "NOW" because it is important to define the file's date but I changed the line that was screw up the results. As I was putting the final file in a variable called $FILE, I always had only on file as output. As soon as I specify the $file, the script start to compress by file. To keep things organized, I put the Date command inside the file's name. Now is complete. Everything the script supposed to do, it finally does.


#!/bin/bash

#Create a reference file
touch -d -20days "/tmp/20dayref.$$"

#Go to the directory in which my files resides
cd /home/pendrive

#Looking for file with specific characteristics
find . -type f  -name 't*'  -print | while read file

#if found, do
do
#If file is newer than the reference file, and if has the specific characteristics
    if [[ ("$file" -nt "/tmp/20dayref.$$") && ( "$file" =~ \.txt$) ]]

    then

#Compress the file using the current date and some specific information

echo "File": $file " is newer  than 20 days"
    echo "Compacting...."
    NOW=$(date +"%m-%d-%Y")
    tar -cz -f "$file".$NOW.MyFile.tar.gz  "$file"

#For clean up metter, delete original  files
    echo "Deleting original backup file...": $file
    rm $file

#If file is older than the reference file

elif [[ "$file" -ot "/tmp/20dayref.$$" ]]

then

#Delete it

    echo "File": $file "is older than 20 days"
    echo $file
    echo "Deleted  permanently...."
    rm $file

else
#If nothing is found to do, just print the success message
echo "Job successfully completed!!!!"

    fi
done

Litle Bit of Shell Script

I've written posts about Python and Python is in fact a great programming language. But, recently I needed solve a situation in which Shell Script was more indicated:

Thanks to the excellent forum about Script :

http://www.unix.com/

Instead of write a whole new post, I'm gonna put here the post I put there. The conclusion, let´s say:


"I'm sharing my code here. Sure it is not elegant but it is doing exactly what I need. So, it is useful !
I have a server that makes backup each 7 day in a FTP server. I want to keep only 3 files and compacted.
The first time that this code will be executed, let´s say 7 days from here, it is expected that will have one file on the FTP server. Then, the script will only compact it.

Seven day after and the script will run again. This time, we will have two files : A new backup file from the server and a .gz file created last time.
I want to keep the .gz, since it has not 20 days yet and I want it compacted.

Later on, there will be situations which we will have a new backup that needs to be compacted, .gz files that need to be kept and .gz file older than 20 days that needs to be deleted.

The FTP should be managed like this way:

backup files coming every 7 days.
Only new backup files being compacted 
files .gz newer than 20 days keeps untouched
files .gz older than 20 days being deleted

By deleting file older than 20 days, allows to me at least 3 backup files on the FTP server. This is more than necessary for my needs.Another point is that this FTP server receives files from other servers as well. Then it is necessary to verify which file I need to handle exactly"

First, I coming to the forum asking for help. I was trying to accomplish the same task but I was using a different approach and an inadequate one.
 I was using "for" and I was trying to get the variable generated from:

 files=($(find . -type f -name 't*' -mtime +"$days"))

if [ $? = "0"]

As explained by someone on the forum:

"The $?  will change after every command, so within the loop you can't depend on it. On top, the second if [[ $? ... ]] 's result is unpredictable at all. To do several tests on the result of a single command, assign its $?  to a variable and test against this."

 This is true and I got stuck trying to solve it.

Then, someone else proposed to create a temporary with the age of 20 days and use it as comparison. It works very well. Maybe I will never get to that by myself.

It was very interesting Challenge!!!

#!/bin/bash

# Create a temp reference file:

touch -d -20days "/tmp/20dayref.$$"


cd /srv/ftp

find . -type f  -name 't*' -print | while read file

//backup file starts with 't'

do

    if [[ ("$file" -nt "/tmp/20dayref.$$") && ( "$file" =~ \.txt$) ]]

//I am using .txt as example. It must reflect your backup extension.

    then

 #file is younger --append to archive


    echo "File": $file " is newer  than 20 days"
    echo "Compacting...."
    NOW=$(date +"%m-%d-%Y")
    FILE="test-Backup.$NOW.tar.gz.$$"
    tar -cz -f "$FILE" "$file"
    echo "Deleting ...": $file
    rm $file


elif [[ "$file" -ot "/tmp/20dayref.$$" ]]

then


 #file is old delete it

    echo "File": $file "is older than 20 days"
    echo $file
    echo "Deleted  permanently...."
    rm $file

else

echo "Job successfully completed!!!!"

    fi

done

Really getting stated with Python

Well, looks like my decision in starting again AND with Python was the right one. I am loving it.
As my first post with 'hands on' will be a very simple code taken from an excellent material I found on the Internet: "Hacking Secret Ciphers with Python with"
 Despite the pretentious title, the material if extremely newbie and very well written. I am expecting to learn a lot about coding and security.
 After explain many concepts about Python, the author presents a very simple code:

#Getting starting with Hacking ciphers
message = 'This message intend to be inverted'
inverted = ''
i = len(message) -1
while i>=0:
    inverted = inverted + message[i]
    i = i -1
   print(inverted)

As the book talks about cryptography and Cipher, this little program aims to perform a very simple way to add a very little security layer at the information. We are just inverting letters inside the message. For sure this is not considered to be a form of security. But, the idea here is start handling code in order to understand its utility in getting security information through the network.

Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb 24 2015, 22:43:06) [MSC v.1600 32 bit (Intel)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> ================================ RESTART ================================
>>> 
detrevni eb ot dnetni egassem sihT
>>> 

I'll try to explain this simple code. Actually to me even this code is not that simple. In short, what it does is at first the variable named message receive the value 'This message intend to be inverted'.
Every time you create a variable, you are actually reserving a memory space and putting there a value. In this case, the value is a "String". In Python, string can be written inside simple quote or double quote.
 If I put something like print(message) I'll retrieve the value in the memory and print will show the phrase.
 Moving down to the code, we have another variable named inverted. This variable has no value. We have just allocated a space in the memory and let it empty.The idea is use this empty slot in conjunction with the variable message in order for invert the phrase.
 Moving down, we can see a new variable name "i". The i's value will be a Python's function named len(). This function has the ability to return an integer representing how many characters there are in the string.
 To prove it, we can change our code:

#Getting starting with Hacking ciphers
message = 'This message intend to be inverted'
inverted = ' '
i = len(message) -1
print(i)
while i>=0:
    inverted = inverted + message[i]
    i = i -1
print(inverted)

We just inserted a print(i) after i = len(message) -1

The output can be seen bellow:

Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb 24 2015, 22:43:06) [MSC v.1600 32 bit (Intel)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> ================================ RESTART ================================
>>> 
33
detrevni eb ot dnetni egassem sihT
>>> 
First, it shows how many characters has the string. Then, it shows the string inverted.

We can do one more thing:

#Getting starting with Hacking ciphers
message = 'This message intend to be inverted'
inverted = ' '
i = len(message) -1
print(i)
while i>=0:
    inverted = inverted + message[i]
    i = i -1
    print(message)
print(inverted)

>>> ================================ RESTART ================================
>>> 
33
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
This message intend to be inverted
detrevni eb ot dnetni egassem sihT
>>> 
I just add a print after  i = i -1 and we can see  the code inserting the phrase in the memory as much times as the amount of character in the string.

We can also discriminate which character is in a specific position:

#Getting starting with Hacking ciphers
message = 'This message intend to be inverted'
inverted = ' '
i = len(message) -1
print(i)
print(message[11])
while i>=0:
    inverted = inverted + message[i]
    i = i -1
print(inverted)


>>> ================================ RESTART ================================
>>> 
33
e
detrevni eb ot dnetni egassem sihT
>>> 

We are showing how many characters there are in the whole string and which character is in the position 11 of the memory. In this case the character "e".


The last one is far more interesting:

#Getting starting with Hacking ciphers
message = 'This message intend to be inverted'
inverted = ''
i = len(message) -1
print(i)
print(message[11])
while i>=0:
    inverted = inverted + message[i]
    print(i, message[i], inverted)
    i = i -1
print(inverted)

This produce the following output:

Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb 24 2015, 22:43:06) [MSC v.1600 32 bit (Intel)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> ================================ RESTART ================================
>>> 
33
e
33 d d
32 e de
31 t det
30 r detr
29 e detre
28 v detrev
27 n detrevn
26 i detrevni
25   detrevni 
24 e detrevni e
23 b detrevni eb
22   detrevni eb 
21 o detrevni eb o
20 t detrevni eb ot
19   detrevni eb ot 
18 d detrevni eb ot d
17 n detrevni eb ot dn
16 e detrevni eb ot dne
15 t detrevni eb ot dnet
14 n detrevni eb ot dnetn
13 i detrevni eb ot dnetni
12   detrevni eb ot dnetni 
11 e detrevni eb ot dnetni e
10 g detrevni eb ot dnetni eg
9 a detrevni eb ot dnetni ega
8 s detrevni eb ot dnetni egas
7 s detrevni eb ot dnetni egass
6 e detrevni eb ot dnetni egasse
5 m detrevni eb ot dnetni egassem
4   detrevni eb ot dnetni egassem 
3 s detrevni eb ot dnetni egassem s
2 i detrevni eb ot dnetni egassem si
1 h detrevni eb ot dnetni egassem sih
0 T detrevni eb ot dnetni egassem sihT
detrevni eb ot dnetni egassem sihT
>>> 

It prints the total number of character, the eleven character and each memory position with its respective value.

And this is it. This simple code is able to read the string, count how many characters it has, decrease it one by one and put each value in the memory and show it inverted.
 According to "while", "i" must be greater than or equal to zero. This is the trigger to the code stop the process and show the message.
 The result is quite simplistic but the idea is great. In a so simple code we can see lots of concepts surrounding this amazing programming language.

Getting started with Coding

This is not the first time I decide to start with Coding. Since the university where I was presented to Java, I have made some approaches with Shell and C. I have gave up from both.
 The fact is, for some reason I don't know, I have some difficult to dedicate all my attention in learning coding. I feel like when I was in the middle school learning math. I was not that bad, actually I was good,but, I have had to spend a lot of energy to stay focus. If I was able to stay focus since the beginning of a new subject in math, I was able to compete with those who had much more talent than me. Different from any other subject  with a few amount of time and energy I was able to go for it and have a nice score.
 I feel the same when it comes to coding. I had not a good experience with Java in the university and I hated to have Java in a Computer administration course.
 The reason why I decided to try again is because there is always a voice inside me saying to learn it. Actually, I can do my job very well without knowing any programming language, I did it so far, but, I realize that to go farther and really make the difference, I need to know at least one scripting programming language.
 With that in mind, I decide to try again and this time I choose Python. Python looks a lovely Programming language. It can be defined as a scripting language and looks far more easier than Java or C. I know that if a programmer read this post he would say something like "you need to learn the logic", programming language is just a tool to use the logic. Ok, I agree, but, I don't see any problem in get more comfortable with one tool than other. As I see so far, Python looks really great.
 I am really excited about it. I feel like I finally found something to start. As long as I can keep focus, I believe I can learn it and have success using it during my jobs. I have seen Python inside boxes I have access to. Cisco boxes are full of Python scripts. I know I can not change it but I can understande it and maybe getting more comfortable and easy my pain in some situation.
 I've read about nice things related with Data centers automation and it is all about scripting. Water it down can  be the next step I need to become more and more successful in my profession. That's I am always looking for.