Stop reinventing `make` in your scripts

From time to time, I find myself writing scripts like this:

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for file in *.mp3; do
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  ffmpeg -i "$file" "${file%.mp3}.opus" & # run in parallel
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done

Then I want more, controlling the number of processes or something.

However I realized I’m actually reinventing make at last.

So here is the makefile equal to the above script.

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SRCS = $(wildcard *.mp3)
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OBJS = $(SRCS:.mp3=.opus)
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%.opus: %.mp3
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  ffmpeg -i $< $@
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out: $(OBJS)
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.PHONY: out