bash script

amboxer21 · 11-16-2013, 05:42 PM

I had a lot of fun writing this. It's been awhile due to work, dirt bike racing and running 5k's. Work(commercial roofing) is slowing down since the winter is drawing near, tomorrow is the last dirt bike of the season for the north east US. So I am picking programming up once again. Man, it has been awhile!

I downloaded an anime series called Bleach from TPB. They all had mkv extensions and I wanted to convert them all to avi. A boring task if done manually by hand. One by one. So I decided to break open a terminal and write a script for it. Inside the directory, there are 16 files that look like this -> Bleach - 137 -.mkv

I wanted to take the spaces out to prevent problems with the script, replace the hyphens with underscores and then run them through an mkv2avi script I took off the internet for conversions.

Anyway, here is the finished product.

Code:

for i in *.mkv; do mv "$i" $(echo $i | sed 's/\(.[-]\)./\_/g;s/_mkv/.mkv/g'); done; for i in *.mkv; do bash mkv2avi "$i" $(echo "$i" | sed 's/\([0-9]_\)\([0-9]_\)\(.mkv\)/\1\2\.avi/g'); done

I figured I would post it here and see if anyone else wants to give it a try. I don't know about y'all but I enjoy writing scripts any chance I get! I love the challenge and it helps keep my skill up to par. Even sharpens them, depending on the OP's skill set(which mine is rather noobish lol). Again, if anyone wants to try and compact it, refine it, do it better, etc. I would love to see!!

unSpawn · 11-16-2013, 06:40 PM

Do this once:

Code:

chmod 0755 mkv2avi

...and then:

Code:

# "while" loops are better wrt IFS and all that:
find /some/path -type f -iname \*.mkv | while read ITEM; do
 # kind of like 'tr -s' ';' but then in BASH:
 NEWNAME=(${ITEM}); NEWNAME=${NEWNAME[@]}; mv "${ITEM}" "${NEWNAME// /_}"
 # ...and since the script is executable now you can:
 mkv2avi "${NEWNAME// /_}"
done

ntubski · 11-16-2013, 07:14 PM

Code:

# "while" loops are better wrt IFS and all that:

That's only true when you try to read the output of a command with for; a for loop over a glob expression has no problems with IFS or other strange filename characters.

You may want to shopt -s nullglob to get reasonable behaviour in the case where no files match the glob though.

grail · 11-17-2013, 06:38 AM

I am not sure I follow the original code logic?? Apart from the fact I do not see why there are 2 for loops, surely one was enough, but the seds in both loops would seem to be flawed to me, based on what was written as the original brief?

Quote:

I wanted to take the spaces out to prevent problems with the script, replace the hyphens with underscores and then run them through an mkv2avi script I took off the internet for conversions.

If we use the example given -: Bleach - 137 -.mkv

The first for loop sed -:

Code:

sed 's/\(.[-]\)./\_/g;s/_mkv/.mkv/g'

Firstly, the use of a back reference and escaping the underscore, none of these are required.

Now the output of this looks nice, but it does not meet the brief as we are to remove spaces and replace hyphens with underscores, however, this removes any character, followed by a hyphen, followed by any
other character and replaces the lot with an underscore. Yes you know the format of the original string so using any character instead of a space either side of a hyphen makes a little sense, but,
being that you now have to add an additional sed change to allow for the fact that you turned a period into an underscore (not in the brief), I consider this lazy coding.
So the current output is:

Code:

Bleach_137.mkv

Spaces removed (check), hyphens replaced with underscores (wrong), we started with 2 hyphens and finished with 1 underscore. Again, format wise I understand, but based on the brief, this is wrong.
So based on the known format and the brief, the following would produce what was asked for:

Code:

sed -r 's/[ -]+/_/g'

This would produce:

Code:

Bleach_137_.mkv

Whilst not the 'desired' outcome, it is what was asked for.

The second for loop sed:

Code:

sed 's/\([0-9]_\)\([0-9]_\)\(.mkv\)/\1\2\.avi/g'

We can look at the affect on both the current and the requested output:

1. Current (Bleach_137.mkv) -: changes - - nothing

2. Requested (Bleach_137_.mkv) -: changes - - nothing

Reasons for no changes in either, the sed is looking for a digit followed by an underscore followed by a digit and another underscore. As we can see from both examples, this pattern appears nowhere. Cannot really assist with this one as apart from wanting to change 'mkv' to 'avi' I am not sure what the other change requirement is?

I will say that for sed, if you use -r it saves the need to escape all of your round brackets for back references and that the saving of '.mkv', which is any character followed by 'mkv', is
also not required here.

Lastly, as pointed out by unSpawn, if you wish to improve your bash skills, then sed is not required as parameter substitution can perform the changes you are looking for (caveat: except the last sed as
at this stage we are not aware of its requirement).

Hope some of that helps

amboxer21 · 11-18-2013, 02:04 PM

Quote:

Originally Posted by grail

The second for loop sed:

Code:

sed 's/\([0-9]_\)\([0-9]_\)\(.mkv\)/\1\2\.avi/g'

We can look at the affect on both the current and the requested output:

1. Current (Bleach_137.mkv) -: changes - - nothing

2. Requested (Bleach_137_.mkv) -: changes - - nothing

Reasons for no changes in either, the sed is looking for a digit followed by an underscore followed by a digit and another underscore.

Thats because i was using this to genrate files to test with and forgot to change the sed line to accommodate the actual name.

Code:

for i in {1..10}; do touch "$i"\ \-\ "$i"\ \-\ .mkv; done

Quote:

Originally Posted by grail

Lastly, as pointed out by unSpawn, if you wish to improve your bash skills, then sed is not required as parameter substitution can perform the changes you are looking for (caveat: except the last sed as
at this stage we are not aware of its requirement).

Hope some of that helps

Yes everyone here has said something helpful and I appreciate the feedback. Like ive said i have done any programming since the beginning of the year. I'm just getting back into it now.