Feature #12695: File.expand_path should resolve ~/ using /etc/passwd when HOME is not set

• Status: Closed
• Assignee: -
• Target version: -

[fursten (Mårten Svantesson)]

I would expect a call like File.expand_path('~/.ssh/known_hosts') to work even though HOME is not set.

A reason this is important to fix is that libraries (in my use case Net::SSH) do calls like File.expand_path('~/.ssh/known_hosts'), but this will often fail when the code is run in a unix service, since HOME often isn't set then.
I considered reporting this as a bug, but the current behaviour is actually documented.

[shyouhei (Shyouhei Urabe)]

+1 it makes sense to me.

[nobu (Nobuyoshi Nakada)]

Why doesn't your service launcher set HOME?

[akr (Akira Tanaka)]

I think its good idea.

Although POSIX doesn't specify it for shell, we can define it in Ruby.

[knu (Akinori MUSHA)]

Makes sense. Ruby knows how to resolve ~user, so you may well expect it to resolve ~ as well given that the login name is identified.

[knu (Akinori MUSHA)]

Bash seems to do that:

% bash -c 'unset HOME; echo ~'
/home/knu

As far as I tested most other known shells like tcsh, zsh, ash, dash and pdksh do not, but we could follow the best.

Through my testing, I found fish unique in that it automatically defines a missing HOME on startup and then expands ~ simply to $HOME. While it would keep things simple and efficient, Ruby is not a shell after all, and altering the environment would clearly be something unasked for.

I think following Bash should be the way to go.

[nobu (Nobuyoshi Nakada)]

https://github.com/ruby/ruby/compare/trunk...nobu:feature/12695-homedir

[matz (Yukihiro Matsumoto)]

Accepted.

Matz.

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset r56902.

---

file.c: home directory from system

• file.c (rb_default_home_dir): resolve home directory from the
  system database when HOME is not set. [Feature #12695]

[pabs (Paul Wise)]

Does anyone know if this also fixes the Dir.home value? Currently (in 2.3) that doesn't work when HOME is unset either.

pabs@chianamo ~ $ unset HOME
pabs@chianamo /home/pabs $ ruby -e 'print Dir.home'
-e:1:in `home': couldn't find HOME environment -- expanding `~' (ArgumentError)
        from -e:1:in `<main>'

[nobu (Nobuyoshi Nakada)]

This is a new feature of 2.4.

[shyouhei (Shyouhei Urabe)]

• Related to Bug #16787: [patch] allow Dir.home to work for non-login procs when $HOME not set added