as:tldr:40833
as: Assemble a file, writing the output to `a.out`.
$ as ${file-s}
try on your machine
The command "as ${file-s}" is using bash variable substitution and brace expansion.
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"${file-s}" is a form of variable substitution. It expands the value of the variable "file" if it is defined, otherwise, it uses the string "s". So, if the variable "file" is set, its value will be used. Otherwise, the string "s" will be used.
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"as" is just a literal string.
So, the command "as ${file-s}" will effectively replace the placeholder "${file-s}" with either the value of the variable "file" (if it is defined) or the string "s" (if the variable "file" is not defined).
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.