bison:tldr:213f4

bison: Compile a bison definition file.

bison

$ bison ${filename-y}

try on your machine

The command "bison ${filename-y}" is a shell command that typically runs the program called "bison" with a parameter. Let's break down the command:

"${filename-y}" is a parameter expansion. It checks if the variable "filename" is defined or not. If "filename" is defined, it will expand to the value of "filename". Otherwise, it will expand to the letter "y". Essentially, this parameter expansion provides a default value of "y" for the variable "filename" if it is not already defined.
"bison" is a program or command-line tool. Bison is a parser generator used mainly in the context of programming language parsing. It takes a specification of a grammar and produces code in various programming languages that can parse input that adheres to that grammar.

So, putting it all together, the command "bison ${filename-y}" runs the "bison" program with the filename specified by the variable "filename", if "filename" is defined. If "filename" is not defined, it uses the default value "y" as the filename.

This explanation was created by an AI. In most cases those are correct. But please always be careful and never run a command you are not sure if it is safe.

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