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4 months ago
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It seems like you often cd to a new directory. How often?
I have analyzed my fish shell history on a Linux machine where it spans from 2019 to 2025 and has just over 100K entries. If you have seen a fish history file, it looks like a subset of YAML:
- cmd: add-apt-repository ppa:zfs-native/stable when: 1342217584 - cmd: time $pra/memsparkline/memsparkline -- tar cv dataset | lrzip -z -L 3 > dataset.tar.lrz when: 1613894771However, it is not valid YAML. With this in mind, I wrote a script to analyze history line-by-line using Python’s helpful fileinput module.
#! /usr/bin/env python3 import fileinput mkdir = 0 cd_after_mkdir = 0 after_mkdir = None for line in fileinput.input(errors="surrogateescape"): args = line.split() # Ignore quoting. match args: case ["-", "cmd:", "mkdir", path, *_] | ["-", "cmd:", "sudo", "mkdir", path, *_]: path = path.rstrip("/") mkdir += 1 after_mkdir = path case ["-", "cmd:", "cd", path, *_]: path = path.rstrip("/") if path == after_mkdir: cd_after_mkdir += 1 after_mkdir = None case ["-", "cmd:", *_]: after_mkdir = None print(f"{mkdir = }\n{cd_after_mkdir = }")You can download the script and try it yourself. Here is what I get on my machine:
> ./analyze.py ~/.local/share/fish/fish_history mkdir = 1244 cd_after_mkdir = 213213 ÷ 1244 × 100% ≈ 17% of mkdir commands are immediately followed by changing to the new directory. This is for my own user account; for root, I have 10 mkdir and 3 cd_after_mkdir, respectively. The numbers are approximate. The script ignores argument quoting, and my shell history covers time after I replaced mkdir followed by cd. Still, this seems like a lot. Why is there no standard shortcut to perform mkdir followed by cd? It doesn’t seem any prominent shell includes one. By contrast, ll for ls -l and la for ls -la are standard in fish.
I know I didn’t invent mkcd and only adopted it years after reading the first Internet comment that described it. This leads me to suspect the friction isn’t obvious. You realize the standard workflow is tiresome after you start using mkcd. (This means you adopt mkcd at your peril.)
Where does mkcd come from? Multiple discovery is likely because the core idea is so simple. I have searched Hacker News with the official Algolia search and Reddit and textfiles.com using DuckDuckGo and Google. The earliest instances I found were a January 2008 comment by HN user dreish and an April 2010 post “mkcd” by Jack Mottram on the Tumblr blog One Thing Well. The dreish comment uses mkdir -p, but Jack Mottram only replaced mkdir with mkdir -p in May 2010 follow-up “mkcd improved” after a message from a reader, suggesting he didn’t borrow from the HN comment.
Searching Usenet Archives finds a linux.debian.user.german post from 2003 by Robert Michel asking about how to implement mkcd as a Bash alias. Other discussion returned by Usenet Archives search is about burning optical media.
After seeing the recommendation for mkcd enough times, in 2024 I decided to try it. I implemented it for fish and quickly became a fan. Over a year later, I strongly recommend it. You can download my mkcd.fish. Install it to your fish functions directory (likely ~/.config/fish/functions/).
function mkcd --argument name if test (count $argv) -ne 1 printf 'usage: mkcd name\n' >&2 return 1 end mkdir -p $name cd $name end
