runtime-directory-use-xdg-runtime-home

Runtime directory: use $XDG_RUNTIME_HOME

We prefer to have a user's runtime directory in a standard place:

• Use XDG_RUNTIME_HOME environment variable if it's set.
• Otherwise use $HOME/.runtime.
• Append the program command, so the program uses its own subdirectory.

Code:

runtime_home() { out "${XDG_RUNTIME_HOME:-$HOME/.runtime}" ; }; export -f runtime_home;
runtime_dir() { out $(runtime_home)"/$program_command" ; };

Purpose:

• Used for non-essential, user-specific data files such as sockets, named pipes, etc.
• Not required to have a default value; warnings should be issued if not set or equivalents provided.
• Must be owned by the user with an access mode of 0700.
• Filesystem fully featured by standards of OS.
• Must be on the local filesystem.
• May be subject to periodic cleanup.
• Modified every 6 hours or set sticky bit if persistence is desired.
• Can only exist for the duration of the user's login.
• Should not store large files as it may be mounted as a tmpfs.