Redirecionando stderr de um script Ruby não funciona como esperado

Question

Eu tenho um comando que acho que está saindo para stderr , porque quando eu redireciono stdout para /dev/null eu ainda recebo saída impressa na tela.

No entanto, quando eu redireciono stderr para /dev/null , também recebo saída impressa na tela.

Além disso, quando eu redireciono toda a saída para /dev/null , ela funciona como esperado.

Como isso pode ser? O 1> e 2> devem pegar pelo menos parte do &> ?

Um exemplo pode ser visto abaixo:

$ HOME=/tmp/fakehome/ bundle exec bin/fullstop https://github.com/mbigras/fake-dotfiles
stderr output of 'git clone https://github.com/mbigras/fake-dotfiles': fatal: destination path 'fake-dotfiles' already exists and is not an empty directory.
Error running 'git clone https://github.com/mbigras/fake-dotfiles'
checkout dir already exists, use --force to overwrite
$ HOME=/tmp/fakehome/ bundle exec bin/fullstop https://github.com/mbigras/fake-dotfiles 1>/dev/null
stderr output of 'git clone https://github.com/mbigras/fake-dotfiles': fatal: destination path 'fake-dotfiles' already exists and is not an empty directory.
Error running 'git clone https://github.com/mbigras/fake-dotfiles'
checkout dir already exists, use --force to overwrite
$ HOME=/tmp/fakehome/ bundle exec bin/fullstop https://github.com/mbigras/fake-dotfiles 2>/dev/null
stderr output of 'git clone https://github.com/mbigras/fake-dotfiles': fatal: destination path 'fake-dotfiles' already exists and is not an empty directory.
Error running 'git clone https://github.com/mbigras/fake-dotfiles'
checkout dir already exists, use --force to overwrite
$ HOME=/tmp/fakehome/ bundle exec bin/fullstop https://github.com/mbigras/fake-dotfiles &>/dev/null
$ 

Para replicar, clone meu projeto:

➜  ~/D/w/tmp  rm /tmp/fakehome
➜  ~/D/w/tmp  mkdir /tmp/fakehome
➜  ~/D/w/tmp  git clone https://github.com/mbigras/mb-fullstop
Cloning into 'mb-fullstop'...
remote: Counting objects: 150, done.
remote: Compressing objects: 100% (84/84), done.
remote: Total 150 (delta 49), reused 147 (delta 46), pack-reused 0
Receiving objects: 100% (150/150), 24.06 KiB | 0 bytes/s, done.
Resolving deltas: 100% (49/49), done.
Checking connectivity... done.
➜  ~/D/w/tmp  cd mb-fullstop
➜  mb-fullstop master ✓ git checkout fix-git-logging-to-stderr
Branch fix-git-logging-to-stderr set up to track remote branch fix-git-logging-to-stderr from origin.
Switched to a new branch 'fix-git-logging-to-stderr'
➜  mb-fullstop fix-git-logging-to-stderr ✓ HOME=/tmp/fakehome/ bundle exec bin/fullstop https://github.com/mbigras/fake-dotfiles
stderr output of 'git clone https://github.com/mbigras/fake-dotfiles': Cloning into 'fake-dotfiles'...
➜  mb-fullstop fix-git-logging-to-stderr ✓ HOME=/tmp/fakehome/ bundle exec bin/fullstop https://github.com/mbigras/fake-dotfiles
stderr output of 'git clone https://github.com/mbigras/fake-dotfiles': fatal: destination path 'fake-dotfiles' already exists and is not an empty directory.
Error running 'git clone https://github.com/mbigras/fake-dotfiles'
checkout dir already exists, use --force to overwrite
➜  mb-fullstop fix-git-logging-to-stderr ✓ HOME=/tmp/fakehome/ bundle exec bin/fullstop https://github.com/mbigras/fake-dotfiles 1> /dev/null
stderr output of 'git clone https://github.com/mbigras/fake-dotfiles': fatal: destination path 'fake-dotfiles' already exists and is not an empty directory.
Error running 'git clone https://github.com/mbigras/fake-dotfiles'
checkout dir already exists, use --force to overwrite
➜  mb-fullstop fix-git-logging-to-stderr ✓ HOME=/tmp/fakehome/ bundle exec bin/fullstop https://github.com/mbigras/fake-dotfiles 2> /dev/null
stderr output of 'git clone https://github.com/mbigras/fake-dotfiles': fatal: destination path 'fake-dotfiles' already exists and is not an empty directory.
Error running 'git clone https://github.com/mbigras/fake-dotfiles'
checkout dir already exists, use --force to overwrite
➜  mb-fullstop fix-git-logging-to-stderr ✓ HOME=/tmp/fakehome/ bundle exec bin/fullstop https://github.com/mbigras/fake-dotfiles &> /dev/null
➜  mb-fullstop fix-git-logging-to-stderr ✓

    

Answer 1

Esta é uma peculiaridade da metadona usada pelo script. Ele se comporta de maneira diferente, dependendo se a saída padrão e o erro padrão são terminais.

Veja o método initialize de cli_logger.rb . Conforme descrito nos comentários:

A logger that logs error-type messages to a second device; useful for ensuring that error messages go to standard error. This should be pretty smart about doing the right thing. If both log devices are ttys, e.g. one is going to standard error and the other to the standard output, messages only appear once in the overall output stream. In other words, an ERROR logged will show up only in the standard error. If either log device is NOT a tty, then all messages go to +log_device+ and only errors go to +error_device+

Você pode contestar a afirmação de que é "muito inteligente em fazer a coisa certa". Um padrão mais sensato para um módulo de log seria logar para stderr e ignorar stdout.