My ideal command history would let me search the history of every shell but when I hit the up arrow it would only cycle through my current shell's history. In February, I was able to achieve this setup in large part because of a utility called hstr.

What is hstr?

hstr is a neat Bash and Zsh utility that lets you easily search, view, and manage your command history. hstr provides a tool named hh that provides a text interface for manipulating your command history. To see what it looks like check out the README and this video tutorial. If you are running OS X and use Homebrew you can install it by running `brew install hh`.

Making global history searchable but arrows cycle through local history

hstr is a neat tool but my favorite part of my setup is how the global command history is searchable but only a shell's local history is cycled through with the arrow keys. This is achieved by manipulating where history is written and tweaking some environment variables.

The first step is to change your $PROMPT_COMMAND to append your shell's history to a global history file. Below is the snippet that does this from my .bashrc file.

# Whenever a command is executed, write it to a global history
PROMPT_COMMAND="history -a ~/.bash_history.global; $PROMPT_COMMAND"

The next step is to bind a keystroke to run hh, which is what hstr provides, with $HISTFILE pointing to ~/.bash_history.global. I wanted to fully replace the default command history searching (and I use Emacs style keyboard shortcuts) so I've bound these actions to ctrl-r.

# On C-r set HISTFILE and run hh
bind -x '"\C-r": "HISTFILE=~/.bash_history.global hh"'

With those two additions to my .bashrc I've achieved my ideal command history searching. When I hit ctrl-r I'm searching all of my history and yet I only cycle through a shell's local history with the arrow keys. This small addition¹ made my command line productivity higher.

1. My setup was inspired by this StackExchange post.↩