CODEWITHSUNDEEP
rcommand-promptansi-escape
Hugo Raguet
Hugo Raguet

Reputation: 428

buggy ANSI escape sequences in R prompt

When R is run interactively in a terminal which supports colors, it is possible to use ANSI escape sequences in order to put colors in the prompt, such as

options(prompt = "\033[0;31mThis is red\033[0m> ")

enter image description here

Unfortunately, something goes wrong because for long command lines, the line continuation override the prompt instead of being written in the next line. enter image description here The problem gets worse when using several colors, because somehow each escape sequence "takes up some space" in the command line, up to the point that the end of the prompt might overwrite the beginning. On my configuration this happens with for instance

options(prompt = paste("\033[0;31m With \033[0;32m multiple",
                   "\033[0;33m colors \033[0;34m this",
                   "\033[0;35m gets \033[0;36m really",
                   "\033[0;37m wrong! \033[0m"))

enter image description here

Why is it so? Is there a workaround?

PS: This rather old post seems related http://r.789695.n4.nabble.com/Xterm-escape-sequences-in-Prompt-td906375.html

update: with R version 3.6.0 and readline 8.0 (don't know which matters here), most of the above described problem disappeared, but some strange behaviors remain. Accepted answer below resolves everything.

Upvotes: 1

Views: 421

Answers (2)

aleksandr barakin
aleksandr barakin

Reputation: 551

you need to surround each «invisible» color code with special «marks»: \001 and \002:

options(prompt = "\001\033[0;31m\002This is red\001\033[0m\002> ")

for explanation see $ info readline (or this short answer).

Upvotes: 2

Hugo Raguet
Hugo Raguet

Reputation: 428

Gábor Csárdi on the r-devel mailing list says that I cannot easily change this behavior (http://r.789695.n4.nabble.com/buggy-ANSI-escape-sequences-in-R-prompt-td4728671.html). The workaround he proposes is to use a two lines prompt, which suits me well enough.

Upvotes: 0

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