[Tutor] writing sample program that zips files and saves in a backup directory

[David Eric]

On Tue, Oct 13, 2009 at 4:14 PM, Dave Angel <davea at ieee.org> wrote:

> (You top-posted, instead of adding your part to the end.  That's frowned
> upon in a mailing list, at least in this one.)
> (You replied privately, and forgot to CC the tutor list.  I'm forwarding it
> there with my response)
>
>
> David Eric wrote:
>
>> wow thank you
>> yes...youre right i did want to pass a list of strings
>> im copying the sample program and adding my own directories, i missed what
>> the example was trying to show in that instance.
>> as far as the recursive option, you mean the -r would process all
>> subdirectories under /Users?
>> im sorry for being so ignorant on this but what would be an example of an
>> innoucuous script?
>>
>>
>>
>> On Tue, Oct 13, 2009 at 3:23 PM, Dave Angel <davea at ieee.org> wrote:
>>
>>
>>
>>> David Eric wrote:
>>>
>>>
>>>
>>>> doing a python tutorial and one of the assignments says to develop a
>>>> program
>>>> that backsup files to zip files into a backup directory
>>>>
>>>> im using Darwin 10.0.0 unix version:
>>>>
>>>> this is what i came up with thus far, i did copy the sample program
>>>> given
>>>> but made changes for my unix OS:
>>>>
>>>> #!/usr/bin/env python
>>>> # Filename : backup_prog.py
>>>>
>>>>
>>>> import os
>>>> import time
>>>>
>>>> source = '/Users/davidteboul/bin/python'
>>>>
>>>> target_dir = '/Users/davidteboul/backups'
>>>>
>>>> target = target_dir + os.sep + time.strftime('%Y%m%d%H%M%S') + '.gz'
>>>>
>>>> zip_command = "gzip -qr {0} {1}".format(target, ' '.join(source))
>>>>
>>>> if os.system(zip_command) == 0:
>>>>   print('Successful backup to', target)
>>>> else: print('Backup FAILED')
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>> When launching external programs you're not familiar with, you really
>>> need
>>> to do a dry-run test, just to be sure.  It wouldn't have been hard to
>>> come
>>> up with something that trashes your system.  (Ask me, I issued a Unix
>>> command once that was deleting all files in a valuable tree, and the only
>>> thing that saved my bacon was that Unix file I/O was so slow.  It only
>>> did
>>> about two files per second, so I was able to Ctrl-C after only losing
>>> about
>>> 5 files, all of which were quickly recoverable.  The next directory down
>>> would have been a disaster, however, and had it completed, we would have
>>> had
>>> to restore from the previous night's nightly backup, effectively wasting
>>> the
>>> day for most employees.)
>>>
>>>
>>> I see two problems, but since I don't know gzip, there may very well be
>>> more.
>>>
>>> The -r switch on nearly all Unix utilities means "recurse" which means to
>>> process all subdirectories of the starting location.
>>>
>>> The ' '.join(source) takes your source string, and puts spaces as every
>>> second character.  The only thing I can think of you might have meant was
>>> to
>>> pass it a list of strings.  So if source were
>>>  source = ['/Users/davidteboul/bin/python',
>>> '/Users/davidteboul/bin/perl']
>>>
>>> then it'd make sense.
>>>
>>> Anyway, I'd launch some innocuous script, that echoes its arguments,
>>> rather
>>> than trying it directly on gzip.   And of course, I'd look at the man
>>> page
>>> for gzip, to see just what its arguments are supposed to look like.
>>>
>>> DaveA
>>>
>>>
>>>
>>>
>> I haven't used Unix in over 15 years, so I don't remember.  But I think it
> had something like 'echo' that simply echoed its arguments to stdout.  In
> Windows, I'd make a one-line batch file like:
>
> Echo Running %0 script, with parameters %*
>
> or
>
> Echo Running %0 script, with parameters %1, %2, %3, %4, %5
>
> The script could also display things like the current directory, maybe some
> environment variables.  Whatever might be relevant to help see what's going
> on.
>
> The -r switch should mean to process all files in
>  /Users/davidteboul/bin/python, plus all files in any of its subdirectories.
> Not starting at /Users, just starting in that ...../python directory.
>
> HTH
> DaveA
>
> Sorry about the top posting and not CC'ing tutor at python.org
>
>
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