How to use brace expansion ({}) to spread shell command arguments
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Today I was reading a discussion about mv. The linked gist includes a shell custom function that wraps the mv command and adds functionality if the user only provides one argument.
# wrapped mv command which accepts edits to
# the provided file path if only one argument was provided
mv planet.png
planet2.png
planet.png -> planet2.png
It allows for editing the file path of provided first argument interactively. That is very neat by itself.
I went on a read the discussion about this command and learned that the mv command, or to make it clearer, bash/zsh make allow to rename a file with something that looks like a single command.
mv a/very/long/path/file.txt a/very/long/path/renamed.txt
You can shorten the above command to the following:
mv a/very/long/path/{file,renamed}.txt
Common shells will extract the {} pattern into its parts and create separate arguments.
mv a/very/long/path/{file,renamed}.txt
# 👆 becomes 👇
mv a/very/long/path/file.txt a/very/long/path/renamed.txt
Another example is the creation of files that include indices.
touch {1..3}.txt
# 👆 becomes 👇
touch 1.txt 2.txt 3.txt
Shell scripting. 💙 There is always something new to learn.
Edited: Dominik pointed out that this shell feature is called brace expansion.
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