goldfish

This is a basic LRU cache backed by an append-only log file. I use it along with cd, neovim, and fzf, in order to have recently-viewed directories and recently-edited files available via fuzzy search. It's meant to be a more transparent alternative to tools like z, and therefore doesn't try to predict or rank anything. It also supports multiple caches via the --cache flag.

goldfish implements first-class support for caching directory and file paths, in the sense that it will a) canonicalize paths and b) check if the path is a file or directory before storing it in the cache. This means the paths should be valid from any working directory, so you can always cd to or edit them. This behavior can be enabled by passing the --type (-t) flag to goldfish put, e.g.

> goldfish --cache files put --type file src/foo.rs
> goldfish --cache files put --type file src/
> goldfish --cache files get
/home/nwtnni/projects/example/src/foo.rs

Usage

goldfish is fairly low-level and meant to be called from a shell script or alias. For example, here's the Bash function I use to change directories:

# Open a directory, list its contents, and cache its path.
#
# If no directory is provided, then use `fzf` to select from the directory cache.
o() {
  if [ -z "$1" ]; then
    dir=$(goldfish --cache directories get | fzf)
    if [ ! -z "$dir" ]; then o "$dir"; fi
  else
    cd "$1" && ls && goldfish --cache directories put --type dir "$1"
  fi
}

More detailed options can be viewed with the --help flag, i.e. goldfish --help.

Installation

Currently requires a Rust installation, and is only available from either:

1. crates.io

> cargo install goldfish

2. Building from source

> git clone https://github.com/nwtnni/goldfish.git
> cargo build --release
> ./target/release/goldfish

Implementation

Log entries are just the data followed by a u16 length footer. This allows append operations to blindly write to the end of the file. Reading the log is done backwards, starting at the last two bytes and seeking back to get each piece of data, which allows us to avoid reading the whole file and efficiently build the set of most recent entries.

(I'm not entirely sure what performance impact reading a file backwards has on, say, caching or prefetching. This would require some benchmarking.)

Disclaimer

There are several articles stating that goldfish actually have decent memory spans, contrary to the popular myth, but I couldn't find many sources. The closest I found was this radio transcript and this science project.