Proposal for BiDi in terminal emulators

Richard Wordingham via Unicode unicode at
Thu Jan 31 03:03:12 CST 2019

On Wed, 30 Jan 2019 20:35:36 -0500
"Mark E. Shoulson via Unicode" <unicode at> wrote:

> On 1/30/19 8:58 AM, Egmont Koblinger via Unicode wrote:
> > There's another side to the entire BiDi story, though. Simple
> > utilities like "echo", "cat", "ls", "grep" and so on, line editing
> > experience of your shell, these kinds. It's absolutely not feasible
> > to add BiDi support to these utilities. Here the only viable
> > approach is to have the terminal emulator do it.  
> How will "ls -l" possibly work?  This is an example of the "table" 
> layout you were already discussing.

I think the answer is that it will use the same trickery as with a
default setting for the --color argument.  Colour codes are emitted
only when the output is a terminal.  Presumably the same would go for
Bidi controls.

> I think us command-line troglodytes just have to deal with not having
> a whole lot of BiDi support.  There's simply no way any terminal
> emulator could possibly know what makes sense and what doesn't for a
> given line of text, coming from some random program.  Your "grep"
> could be grepping from a file with ANY layout, not necessarily one
> conducive to terminal layout, and so on.

So how do editors work now?

To avoid confusion, you will have to work with the terminal set to
having LTR paragraphs (or RTL instead); that is how Notepad works.


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