Hyperlink escape sequence causes bad output in Ubuntu 16 LTS terminal

[jay]

I did this

curl --head https://www.google.com

In Ubuntu 16 LTS terminal the location header has unrecognized escape sequences and duplicate URL.

location:�]8;;https://www.google.com/�\ https://www.google.com/
�]8;;�\content-type: text/html; charset=UTF-8

/cc @dfandrich

[dfandrich]

What terminal emulator does this use? On all the ones I tried, the escape sequence is either interpreted correctly or ignored and not displayed.

[jay]

Gnome Terminal 3.18.3 + VTE 0.42.5

[bagder]

@dfandrich is this only because of an older gnome terminal and we can just ask users to run a later version or is there anything more clever we can here?

[dfandrich]

OSC 8 support was added to Gnome Terminal 6 years ago in ver. 3.25.1. There's a list tracking support in terminal emulators on this page. The OSC 8 spec also says

Any terminal that correctly implements OSC parsing according to ECMA-48 is guaranteed not to suffer from compatibility issues. That is, even if explicit hyperlinks aren't supported, the target URI is silently ignored and the supposed-to-be-visible text is displayed, without artifacts.

It sounds like there may have been a bug in Gnome Terminal that didn't do this, but other terminal emulators, even those that don't support OSC 8, should ignore the extra data and that is what I found in my testing. That spec page lists four terminal emulators that still didn't work properly as of 3 years ago, but all of them are working (mostly) today in their latest versions.

I can't think how we could easily and reliably detect whether a terminal emulator is buggy or not and dynamically enable this. xterm-style answerback strings might theoretically do it if those were still a thing, otherwise it would take linking with an X11 library and even that wouldn't work all the time. My suggestion would be to just use --no-styled-output on those few cases where it doesn't work, or better yet, upgrade your terminal emulator since there aren't any known buggy implementations left according to that page.

[jay]

That page also says VTE versions up to 0.48.1 (6 years ago) have bugs so I've submitted #11071 to test VTE_VERSION env var