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65 lines
1.6 KiB
Text
65 lines
1.6 KiB
Text
= Path opearations
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Paths can be concatenated with each other to produce a new path.
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[source]
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....
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nix-repl> /home/wombat + /bin/sh
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/home/wombat/bin/sh
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nix-repl> :t /home/wombat + /bin/sh
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a path
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....
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[IMPORTANT]
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====
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Relative paths become absolute when they are parsed, which occurs before concatenation.
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This is why the result in the example below is not `/home/amy/file.txt`.
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[source]
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....
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nix-repl> /home/wombat + ./file.txt
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/home/wombat/home/amy/codeberg/nix-book/file.txt
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....
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====
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A path can be concatenated with a string to produce a new path.
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[source]
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....
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nix-repl> homePath + "/file.txt"
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/home/wombat/file.txt
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nix-repl> :t homePath + "/myfile.txt"
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a path
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....
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[NOTE]
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====
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The Nix reference manual says that the string must not "have a string context" that refers to a store path.
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String contexts are beyond the scope of this book;
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for more information see https://nixos.org/manual/nix/stable/language/operators#path-concatenation.
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====
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Strings can be concatenated with paths, but with a side-effect that may surprise you:
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if the path exists, the file is copied to the Nix store!
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The result is a string, not a path.
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In the example below, the file `file.txt` is copied to `/nix/store/gp8ba25gpwvbqizqfr58jr014gmv1hd8-file.txt`
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(not `/home/wombat/nix/store/gp8ba25gpwvbqizqfr58jr014gmv1hd8-file.txt`).
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[source]
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....
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nix-repl> "/home/wombat" + ./file.txt
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"/home/wombat/nix/store/gp8ba25gpwvbqizqfr58jr014gmv1hd8-file.txt"
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....
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The path must exist.
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[source]
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....
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nix-repl> "/home/wombat" + ./no-such-file.txt
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error (ignored): error: end of string reached
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error: getting status of '/home/amy/codeberg/nix-book/no-such-file.txt': No such file or directory
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....
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