asciinema-rec_script

Record 💭 comments and ❯ commands from from shell scripts in addition to their output.

This is done by building a version of the original script that surfaces all the comments and commands by also echoing them to the screen.

Then passing that augmented script to asciinema's rec --command command.

Motivation

The asciinema tool is an awesome terminal session recorder.

And it has a rec [filename] command with a -c --command=<command> option.

This specifies a command to record (other than the default of $SHELL)

So given an (executable) script screencasts/demo-date_maths:

#!/usr/bin/env bash
## Date maths

# The `date` command can be used to retrieve the:
#  * *day of the week* using the `%l` option
day_of_the_week=$(date +%l)

#  * *hour of the day* using the `%u` option
hour=$(date +%u)


# Now, can you guess what we're going to do with those two numbers?
# 🤔...
sleep 3

# We're going to add them together!
echo $((day_of_the_week + hour))

We can use asciinema's rec to make a recording:

asciinema rec --command screencasts/demo-date_maths

However that recording is going to lose a bunch of context from the script and end up looking something like this:

If, however we instead used this command:

asciinema-rec_script screencasts/demo-date_maths

Without any effort we can end up with a recording like this:

Getting Started

Installation:

Place asciinema-rec_script somewhere in your $PATH.

Requirements:

• asciinema (installation)
• bash
• (optional) bat (installation)
  • A cat clone to provide syntax highlighting

Example Usages:

• asciinema-rec_script ./screencasts/demo-date_maths
  • When called with no extra arguments, the tool will pass asciinema rec a filename of ./screencasts/demo-date_maths.cast to place the recording in
  • (Nb. the filename is derived from the source script by attaching a .cast extension.)
• ./screencasts/demo-date_maths.asc
  • Will take advantage of the shebang line #!/usr/bin/env asciinema-rec_script in the .asc script
  • (ie. allowing the input script to be run as its own command, without having to pass it as an argument to asciinema-rec_script)
• ./screencasts/demo-date_maths.asc --
  • When called with -- the tool will allow asciinema rec to receive no additional arguments
  • (ie. allowing it to maintain its default behaviour of uploading screencasts to https://asciinema.org)
• ./screencasts/demo-date_maths.asc --help
  • Will also pass any additional arguments it gets to asciinema rec
  • (so eg. --help will show all the asciinema rec [options])
• SLEEP=0 ./screencasts/demo-bash_functions.asc
  • (env vars can be passed into the script in the regular way)
  • (to eg set PROMPT="$ ", PROMPT_PAUSE=5)
• bash ./screencasts/demo-date_maths.asc
  • Nb. It should also be possibe to execute the .asc script in your $SHELL as a regular bash script
  • (Maintaining this compatability means that the .asc file won't require any special commands that a regular shell script wouldn't already have in it. Which hopefully results in regular shell scripts resulting in half-decent looking recordings.)

(Nb. the .asc extension ("ASCiinema") is not strictly necessary, but gives some uniformity.)

How it works

asciinema-rec_script (written in bash) reads from the file passed to it one line at a time and will detect:

• ❯ lines of code (syntax highlighting them as bash code)
• 💭 comments (syntax highlighting them as markdown)
• blank lines (preserving whitespace)
• 💬 and some other special lines

It uses meta-programming to build an augmented version of itself from each of these lines storing them in a temporary augmented_script file.

And finally it passes that file (and any other arguments specified on the command line) to asciinema run --command <augmented_script> for it to make a recording.

Nb. although the .asc scripts are used to produced asciinema recordings its expected that these files can also be run in bash/zsh

eg.

❯ source screencasts/demo-bash_functions.asc
a='a 0', b='b 0', c=''
-> f1(a='a 0', b='b 0', c='')
-> f1(a='a 0', b='b 0', c='')
BEFORE: a='a 0', b='b 0', c=''
-> f1(a='a 1', b='b 1', c='c 1')
AFTER : a='a 1', b='b 1', c='c 1'
BEFORE: a='a 0', b='b 0', c=''
-> f1(a='a 1', b='b 1', c='c 1')
AFTER : a='a 0', b='b 0', c=''
-> f1(a='a 1', b='b 2', c='c 2')
-> f1(a='a 1', b='b 0', c='c 2')
Sun Oct 17 20:56:56 AEDT 2021
-> f1(a='a 1', b='b 0', c='Sun Oct 17 20:56:56 AEDT 2021')
BEFORE: a='a 0', b='b 0', c=''
-> f1(a='a 1', b='b 3', c='c 3')
AFTER : a='a 0', b='b 0', c=''
-> f2(a='a 4', b='b 4', c='Sun Oct 17 20:56:56 AEDT 2021')
-> f2(a='a 4', b='b 4', c='Sun Oct 17 20:56:56 AEDT 2021')
-> f2(a='a 4', b='b 4', c='c 4')

Limitations

As the .asc is read in one line at a time, making it difficult (if not impossible) to execute multi-line commands in these shell scripts.

The two workarounds I could think of were:

1. making every multi-line command fit on one line

• So this:

  f1() {
    echo "-> f1(a='$a', b='$b', c='$c')"
  }
  

• would have to be manually edited in the .asc file to this:

  f1() { echo "-> f1(a='$a', b='$b', c='$c')"; }
  

2. inline the multi-line code from a source command:

• So something like this:

  source "${script%.asc}/f1.1"
  

• could be used (eg. here) to source this file but be seemlessly displayed in the recording as:

  f1() {
    echo "-> f1(a='$a', b='$b', c='$c')"
  }
  

Similar & Related Projects

• https://github.com/garbas/asciinema-scenario

Also included

asciinema-gh

This tool provides a command line playack menu of screencasts which it pulls from github repos.

It works with both public & private github repos.

(Nb. The recordings that appear in the menu don't necessarily have to be made using asciinema-rec_script, but the menu will filter out all the .asc files from that directory.)

Requirements:

• asciinema
• gh
• jq

Example Usages:

• asciinema-gh zechris/asciinema-rec_script
  • search for .cast files in https://github.com/zechris/asciinema-rec_script/tree/master/screencasts
• REF=v0.9.0 asciinema-gh zechris/asciinema-rec_script
  • (which can be used with a github REFs like release tags eg. v0.9.0)
• REF=first_pr asciinema-gh zechris/asciinema-rec_script
  • (or branch names eg. first_pr)
• asciinema-gh spectreconsole/spectre.console docs/input/assets/casts
  • (NB. a path can also be specified if the screencasts aren't found in the default ./screencasts)
• echo 26 | screencast_dir=docs/input/assets/casts asciinema-gh spectreconsole/spectre.console
  • (to pre-select number 26 from the menu)