asciicast

Turn R scripts into terminal screencasts

asciicast takes an R script and turns it into an asciinema cast. It can simulate typing, and records all terminal output in real time as it happens.

Features

• Input is an R script, output is a v2 asciicast recording.
• Record all terminal output in real time, as it happens.
• Simulate typing in the commands, with a configurable, randomized speed.
• Alternatively, whole comment blocks or expressions can just appear on the screen.
• Convert casts to SVG images using svg-term. The package comes with its own svg-term bundle, no external dependencies are needed.
• Render a single frame of a cast as an SVG image.
• Configurable delay at the beginning, at the end and between paragraphs.
• HTML widget, to be used in Rmarkdown documents, e.g. in vignettes.
• Read casts from asciinema JSON files (version 2), or from https://asciinema.org directly.
• Special knitr engine to create R markdown files with ascii casts. See the asciicast-demo vignette.
• Create ascii casts in GitHub READMEs via animated SVG files. See an example in inst/examples or the README.Rmd source of the README file you are reading.

Limitations

• asciicast does not work in Windows yet, because of a the lack of a pseudo terminal. Maybe you can try running it on Linux in Docker?
• Recordings are currently real time, so if you “type in” a lot of code/text, that might take a while to record.
• Only syntactically correct R script files can be recorded.
• asciicast redefines option("error") currently, so if you want to set this option in your demo, that won’t work.

Installation

You can install the released version of asciicast from CRAN:

install.packages("asciicast")

Examples

See the inst/examples directory for these examples.

Hello world

The input script:

#' Rows: 10

print("Hello world!")

Asciicast demo in asciicast

Input script that uses asciicast itself:

#' Title: asciicast example recorded in asciicast
#' Cols: 80
#' Rows: 40
#' Empty_wait: 3
#' End_wait: 20

# <<
# An example for using asciicast, recorded in asciicast itself!

# First, save the R code you want to run, in a script file.
# The file can contain any code, including interactive code,
# as long as it is a syntactically valid R file.

# Second, perform the recording with the `record()` function.
# We are recording an example file now, that comes with the package.
# <<

src <- system.file("examples", "hello.R", package = "asciicast")
cast <- asciicast::record(src)

# <<
# `cast` is an `asciicast` object, which has some metadata and the
# recording itself:
# <<

cast

# <<
# You can write `cast` to a JSON file that can be played by any
# asciinema player. Or you can write it to an SVG file that can
# be embedded into a web page, or a GitHub README.
# <<

svg <- tempfile(fileext = ".svg")
asciicast::write_svg(cast, svg, window = TRUE)

Errors are recorded

Input script with errors:

#' Rows: 15

# Demonstrate that errors are handled well

library("not-this-really")

traceback()

1+1

Related tools

• asciinema: https://asciinema.org/
• The original terminal session recorder: https://github.com/asciinema/asciinema
• svg-term: https://github.com/marionebl/svg-term, https://github.com/marionebl/svg-term-cli

License

MIT @ RStudio