ZSH-MERGE-HIST
What?
It's a simple command-line utility for merging extended ZSH history files from different sources, while keeping the entries properly ordered by date.
Why?
In my home LAN I have a few servers (made out of old laptops and Raspberries)
with which I interact via SSH and ZSH. I use fzf to pimp my Ctrl + R
(along with setting HISTSIZE to a very large value - currently one million),
which makes it very easy to find the command I need even if I only remember
small parts of the command. More precisely, it's easy to find the command if it
was executed on the machine I'm currently logged into, which resulted in a lot
of irritating copy&paste in cases where I needed to execute the same command on
more than 2-3 servers.
How?
This utility is meant to be run from CRON. When invoked, the app will download history files from all the configured servers via SCP, then parse them all taking into account the peculiar "metafying" that ZSH does. Then the parsed entries are sorted by date and dumped back into ZSH (extended) history file format. Finally, the merged history file is uploaded back to all the configured servers.
(Un)metafying?
One of the peculiarities of the history file format is that it encodes
characters outside of the latin1 encoding with a special character called
Meta with the value of 0x83 (134 in decimal). See
the C implementation of the escaping logic (taken from
ZSH source). Unfortunately, ignoring the issue and copying the Meta char along
with the command text doesn't work, because it makes for invalid UTF8, which is
problematic when dumping the data back to file. So I had to reimplement the
escaping and unescaping logic as part of the app,
in Scala. I believe that implementation is easier
to understand due to pattern matching, but anyway - it works, so it's all good!