Shell – Split a File by Line and Control Resulting File Extensions

Unless I'm missing something, split does split by line if you use -l switch:

   -l, --lines=NUMBER
          put NUMBER lines per output file

so

split -l 1 inputfile

should do what you want.

I am assuming you use Linux and GNU split. If so, you can do this directly with split.

So, how does split work? As with most *nix software, its manual is available by running man split. Specifically, the general usage is

split [OPTION]... [INPUT [PREFIX]]

That means that you can specify the prefix yourself. For example, if you split a file called foo and give the prefix bar:

$ ls
foo
$ split foo bar
$ ls
baraa  barab  barac  foo

As you can see, since a prefix was given to split, it has created the files called bar followed by a suffix (aa to ac in this case). So, in your case, you want to give the name of the file as a prefix:

for f in *mp3; do split "$f" "$f"

But you also want to remove the extension so that splitting foo.mp3 does not result in foo.mp3aa but fooaa. This can be done using bash's string manipulation capabilities by writing ${f%.mp3} instead of simple $f.

Finally, you can use another nifty feature of split to add the extension:

   --additional-suffix=SUFFIX
          append an additional SUFFIX to file names.

So, putting it all together:

for f in *mp3; do 
   split --bytes=2500k --additional-suffix=".mp3" -d "$f" "${f%.mp3}_"; 
done

I ran this in a directory that contained the following files:

aa.mp3  bb.mp3  cc.mp3

And it resulted in these split file names:

aa_00.mp3  aa_02.mp3  bb_00.mp3  bb_02.mp3  cc_00.mp3  cc_02.mp3
aa_01.mp3  aa_03.mp3  bb_01.mp3  bb_03.mp3  cc_01.mp3  cc_03.mp3