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• are reporting a bug others will be able to reproduce and not asking a question. If you're not sure or want to ask a question do so on our Discourse: https://discourse.brew.sh
• ran a brew command and reproduced the problem with multiple formulae? If it's a problem with a single, official formula (not cask) please file this issue at Homebrew/homebrew-core: https://github.com/Homebrew/homebrew-core/issues/new/choose. If it's a brew cask problem please file this issue at https://github.com/Homebrew/homebrew-cask/issues/new/choose. If it's a tap (e.g. Homebrew/homebrew-php) problem please file this issue at the tap.
• ran brew update and can still reproduce the problem?
• ran brew doctor, fixed all issues and can still reproduce the problem?
• ran brew config and brew doctor and included their output with your issue?

What you were trying to do (and why)

Any brew command that passes a URL to open a tab in the web browser fails on Linux. For example, brew home or brew info --github.

What happened (include command output)

The correct web browser command runs, but fails with an error that the display cannot be opened and the tab is not opened.

mike@host:~$ brew home
(google-chrome:32228): Gtk-WARNING **: 20:57:36.156: cannot open display:

mike@host:~$ brew info --github gcc
(google-chrome:32447): Gtk-WARNING **: 20:57:40.127: cannot open display:
  

What you expected to happen

The web browser should open a new tab with the given URL.

The reason is clearly that the DISPLAY environment variable is removed in the sanitized environment that brew runs itself in. If I locally modify brew to include DISPLAY in the list of whitelisted environment variables, then the web page is opened as expected.

Step-by-step reproduction instructions (by running brew commands)

1. Install Linuxbrew on a GNU/Linux system, accept the default installation options.
2. Run any command that tries to open a web page

brew home
brew home gcc
brew info --github gcc
brew search --debian gcc

Output of brew config and brew doctor

mike@host:~$ brew config
HOMEBREW_VERSION: 2.0.1
ORIGIN: https://github.com/Homebrew/brew
HEAD: e32c1515432a938093d5ef1d8c4b4408991873df
Last commit: 29 hours ago
Core tap ORIGIN: https://github.com/Linuxbrew/homebrew-core
Core tap HEAD: 4b962b502dadb8a93e554bb16dbaa19c526bf3a7
Core tap last commit: 6 hours ago
HOMEBREW_PREFIX: /home/linuxbrew/.linuxbrew
HOMEBREW_CACHE: /home/mike/.cache/Homebrew
HOMEBREW_LOGS: /home/mike/.cache/Homebrew/Logs
HOMEBREW_VISUAL: vim
CPU: octa-core 64-bit haswell
Homebrew Ruby: 2.5.3 => /usr/bin/ruby2.5
Clang: 7.0 build 701
Git: 2.20.1 => /home/linuxbrew/.linuxbrew/bin/git
Curl: 7.63.0 => /usr/bin/curl
Kernel: Linux 4.19.0-1-amd64 x86_64 GNU/Linux
bOS: Debian GNU/Linux buster/sid (buster)
Host glibc: 2.28
/usr/bin/gcc: 8.2.0
glibc: N/A
gcc: 5.5.0_4
xorg: N/A
mike@host:~$ brew doctor
Your system is ready to brew.