kacpersh

My friend Kacper told me about an inconvenience that sometimes happened to him - you execute a long running command, then want to do something with the output, but you forgot to redirect it to a file or something, so you have to re-run it all.

The idea is to make the shell/terminal/whatever capture all commands, and make the last command's outputs available to the user easily.

Also, Kacper sounds a bit like "capture". So, it fits.

Screencast

Usage

Download or build kacpersh and put it in your $PATH

Homebrew:

brew tap irth/irth
brew install irth/irth/kacpersh

You can download precompiled kacpersh from the releases page.

Alternatively, install go and compile it yourself:

go build
sudo mv kacpersh /usr/local/bin

Add it to your .zshrc

Currently only ZSH is supported.

echo 'eval "$(kacpersh init zsh)"' >> ~/.zshrc

Run kacpersh and use the _ alias to retrieve the stdout of the last command.

$ kacpersh
$ # this is now running under kacpersh
$ echo -n 'test\nhello'
test
hello
$ _
test
hello
$ _ | grep hello
hello
$ _
hello

Proof of concept

https://gist.github.com/irth/ffba9da0a9a4f6df54f02fe06605f19c

TODO:

v1

• launch users shell (according to SHELL/profile by default) instead of a hardcoded one
• communicate over a unix socket, path to which is passed through an env variable (so that u can have more than one shell)
• generate config for zsh, so that it can be eval'ed in .zshrc easily
• limit the saved buffer size so that it doesn't fill up your ram (for now I hardcoded it to 32MiB)
• allow auto-activation through zshrc

v2

• in-band signalling - this will allow as to implement buffering for performance, as we don't have to keep perfect synchronisation anymore
• see if we can support bash and fish

v3

• a version of _ command that doesn't replace the stored output with its own so that you can do something like this:

$ curl example.com/a/slow/api
first line of output
some more output
hello

$ __ | grep some
some more output

$ __ | grep output
first line of output
some more output

v4

• capture multiple commands instead of just the last one, decreasing the odds of losing data

sometime along the line...

• configuration? (e.g. setting last command buffer limit)