string manipulation in bash ${#:1:$#-1} [duplicate] - bash

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May you please explain what does this mean:
#:1:$#-1
can you provide an exact explanation?

That's a parameter expansion that returns all the positional parameters but the last one.
It's based on ${parameter:offset:length}, where using # as parameter makes it work on positional parameters. The length $#-1 is the number of positional parameters ($#) minus one.
Here's a showcase : https://ideone.com/HKcaNj

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