export XDG_RUNTIME_DIR='$XDG_RUNTIME_DIR'
@domi mkdir '$XDG_RUNTIME_DIR'
or
mkdir "\$XDG_RUNTIME_DIR"
Pretty much every character is valid in linux filenames. I accidentally made a '~' directory in my home directory once and then proceeded to delete most files in my home directory x3
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I would consider it more likely that someone didn't realize that a path is not going to be shell escaped in some configuration (but that might be biased by the kinds of linux setups I see or run).
