extPrompt

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Update: Prof. Duncan Temple Lang, one of the core developers of R, actually gave a simpler way of achieving the same thing:

invisible(addTaskCallback(function(...) { 
                 options(prompt = format(Sys.time(), "[%H:%M:%S] >"))
                 TRUE
                 }))

That almost subsumes the functionality of this package, with one minor shortcoming:

The only difference is that when you hit return at the prompt with no expression, the prompt doesn't change (since there was no task).

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Embed current time in the R prompt.

Usage:

library(devtools)
install_github('musically-ut/extPrompt')
library(extPrompt)

# Gives a prompt like:
# [17:08:10] > 
# instead of just:
# >

You can reset the default prefix by any value you want:

options(prompt='\033[0;38;5;33m[%H:%M:%S] \033[0m> ')

This will, for example, give you a prompt with the time prefixed in blue color.

Rationale

I often find myself accidentally starting a R command without realizing how long it will take to execute. Only after the command has been running for some arbitrary time do I realise that I should have at least wrapped it inside a system.time to get an idea of how long it takes to run.

This plugin solves the problem by appending the approximate start time in form of time-stamps to each command. Now by merely looking at the time-stamps on the R console, one can make a good estimate of how long each command ran.