multi generation daily file backups

[Jeramy]

Be aware this is going to be ugly because I have never written anything in python and am attempting to quickly pick up just enough to solve my problem. I need a way to automate doing about 2 weeks of daily archives of a backup file. I think I have the logic down and have hacked together some code from the help files and some web searches, but I am sure it is not quite right yet. I am still hacking away at it but I figured it was worth asking here for some help too. Here is what I have so far:

#!/usr/bin/env python
import commands,shutil

#get the day of the month as an int in the range of 1-31 using a bash command to use in filenames
day=int(commands.getoutput('date "+%d"'))

#drop the latter half of the month by 15 since I only need 2 weeks of backups
if [ "$day" > "15" ]; then
day -= 15
fi

#create my source and destination filenames using the day number to cycle the files
sfn = r"/volumes/Storage/MediaNet/*saveset.bck"
dfn = r"/volumes/Storage/MediaNet/.bck/" + str(day) + r"backup.bck"

#copy the file into the backup directory
shutil.copy(sfn, dfn)

I am sure my syntax is off and if anyone knows a better way to do the same thing I would gratefully accept any input. Thanks for taking the time to help.

[Beat_Slayer]

Your code will only run on linux. It looks more like a bash script then a python code.

I just don't get if they are multiple files to copy and if it is to copy every day
or id it only 15 of all the backups that there exist.

[Jeramy]

The file "saveset.bck" is a backup file created by another program which overwrites itself daily, making it pretty useless. My objective is to make copies of this file daily after each backup to a sub directory, "/.bck/" with about a week worth of daily copies; in my attempt above these would be named 1backup.bck - 16backup.bck, in theory at least. Once it gets to 15 or 16 (depending on the month) it should start back over at 1 and overwrite the oldest save file. I would have written a bash script to do this if I could have figured out a way to do so. It is likely there is and I just missed it.

If you have a suggestion on how I can do this better, please let me know. My knowledge is fairly limited and I can use all the help I can get. :)

[TrustyTony]

For the day modulo 15 you can use:

## get 0..15 int from current day
from datetime import date
print(date.today().day % 16)

So something like this (if you have pre-existing bck directory in place before hand):

from datetime import date
import os
import shutil

## get 0..15 int from current day
day = (date.today().day % 16)

path = r"/volumes/Storage/MediaNet"
sfn = "saveset.bck"
dfn = "%sbackup.bck" % day

print 'Copying',sfn,'to',dfn

#copy the file into the backup directory
shutil.copy(os.path.join(path,sfn),os.path.join(path,'bck',dfn))
print 'Saved backups are:',', '.join(os.listdir(os.path.join(path,'bck')))

[Beat_Slayer]

A simple example. It's only a example, not a finnished code, but you can try to add to the concept of Tony and we'll see where you get. ;)

f_backup = path_to_file
basename, ext = os.splitext(f_backup)
copy_path = path_to_copy

counter =0
while running:

    if copied == None and os.path.isfile(f_backup) == 1:
        counter += 1
        os.copy(f_backup, copy_path + basename + counter + ext)
        os.remove(f_backup)
        copied = True

    if copied == True and os.path.isfile(f_backup) == 1:
        os.remove(f_backup)
        copied = None

[TrustyTony]

A simple example. It's only a example, not a finnished code, but you can try to add to the concept of Tony and we'll see where you get. ;)

Sorry, not my concept, but concept of posters original " ' Python code ' "

Would probably make sense also to put

from time import sleep ## first lines
### end of script
sleep(24*60*60) # daily

And indent the code in endless while True: loop.

EDIT: The datetime code is the lines until line 10 in original post.

[Beat_Slayer]

I was talking about the datetime code Tony.

When I started writing you didn't had edited your post yet.

[Jeramy]

Wow. Excellent. I can not thank you both enough for the incredibly helpful and quick replies. I think it is working!

I didn't add in the sleep code, I was planning on using crontab to schedule the daily executions. Is there any reason to use one over the other?

Just one question on how it is working though: How does the "date.today().day % 16" work? It appears to give me the right number, but I don't understand how. I am looking it up right now on the python site as well to make sure I understand it.

Thank you both again.

EDIT: I found it and I get it now. That is slick and works well, much better than the cumbersome way I was trying to do it. Thank you!