rotate a "for" loop with 5 variables together

Question

Use a program to create audio files called stem which combines vocals, drums, melody, bass and an audio guide into a single file.

I am trying to create a loop that stores these files and so the application can use it.

Inside the folder I have the files:

a.vocal.m4a a.bateria.m4a a.melodia.m4a a.baixo.m4a a.master.m4a 
b.vocal.m4a b.bateria.m4a b.melodia.m4a b.baixo.m4a b.master.m4a 
c.vocal.m4a c.bateria.m4a c.melodia.m4a c.baixo.m4a c.master.m4a

I tried to spin:

for f in *.vocal.m4a; for g in *.bateria.m4a; for h in *.melodia.m4a; for i in *.baixo.m4a; for j in *.master.m4a; 
do mesclar "$f" "$g" "$h" "$i" "$j" ; 
done

But the tie only works on the last for. I would like a loop that runs all the files "a" after the files "b" and then the "c" and so on.

Answer 1

In shell script, just make a loop by the letters of a up to the letter you want (let’s assume it’s c):

for i in {a..c}
do
    mesclar $i.*
done

This, assuming that in the directory you only have the files you want (if you have any others whose name is a.algumacoisa, it will also be passed to the command mesclar). Also, when using $i.*, the files will be passed in alphabetical order. If you want to restrict the files and control the order, you can switch to:

for i in {a..c}
do
    mesclar $(echo $i.{vocal,bateria,melodia,master}.m4a)
done

In the case, the echo prints the letter, the dot, and then vocal, bateria, etc, in this order. That is, the files are passed in the desired order. And I use the syntax of command substitution so that the exit of the echo is passed to command mesclar.

If instead of a, b, c, etc, the names can be anything (not necessarily a sequence), you can put them separated by comma.

Also, once you have these names, you can compose the command however you want. Using the example of your comment, would be:

for i in {nome,outronome,maisoutro}
do
    mesclar $(echo $i.{melodia,vocal,baixo,bateria}.m4a) -x $i.master.m4a
done

That will call the commands:

mesclar nome.melodia.m4a nome.vocal.m4a nome.baixo.m4a nome.bateria.m4a -x nome.master.m4a
mesclar outronome.melodia.m4a outronome.vocal.m4a outronome.baixo.m4a outronome.bateria.m4a -x outronome.master.m4a
mesclar maisoutro.melodia.m4a maisoutro.vocal.m4a maisoutro.baixo.m4a maisoutro.bateria.m4a -x maisoutro.master.m4a

---

In Python the idea is similar, just use one of the many ways of calling external processes to call the command. Example with os.system:

import os

files = ['vocal', 'bateria', 'melodia', 'master']
for i in 'abc':
    params = ' '.join(f'{i}.{file}.m4a' for file in files)
    os.system(f'mesclar {params}')

Or, with a list of names and the command indicated in the comments:

import os

files = ['melodia', 'vocal', 'baixo', 'bateria']
for i in ['nome', 'outronome', 'maisoutro']:
    params = ' '.join(f'{i}.{file}.m4a' for file in files)
    os.system(f'mesclar {params} -x {i}.master.m4a')

That will call the commands:

mesclar nome.melodia.m4a nome.vocal.m4a nome.baixo.m4a nome.bateria.m4a -x nome.master.m4a
mesclar outronome.melodia.m4a outronome.vocal.m4a outronome.baixo.m4a outronome.bateria.m4a -x outronome.master.m4a
mesclar maisoutro.melodia.m4a maisoutro.vocal.m4a maisoutro.baixo.m4a maisoutro.bateria.m4a -x maisoutro.master.m4a

Answer 2

Use the zip() function. With it you can browse several lists.

>>> letters = ['a', 'b', 'c', 'd', 'e']
>>> numbers = [0, 1, 2, 3, 4]
>>> for l, n in zip(letters, numbers):
...     print(f'Letter: {l}')
...     print(f'Number: {n}')

Letter: a
Number: 0
Letter: b
Number: 1
Letter: c
Number: 2
Letter: d
Number: 3
Letter: e
Number: 4