What does this line means in a shell script?

What does this line means in a shell script?

THIS_SCRIPT=$(readlink -f $0)开发者_开发知识库

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It assigns the path of the script to variable THIS_SCRIPT. I checked the readlink manpage, the -f option follows the symlinks in path (if they exist)

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$(...) means run the command within and return the output as a string. =, as you probably already know, assigns a string to a variable.