TIL on semikolan

The Markdown reference

Wed, 22 Jul 2026 00:00:00 +0000

Headings

H1 · Heading one

H2 · Heading two

H3 · Heading three

H4 · Heading four

H5 · Heading five

H6 · Heading six

Inline formatting

Text can be bold, italic, bold italic, ~~struck through~~, or inserted. You can highlight a phrase to draw the eye, drop in inline code, and link to another post.

Pretty-print JSON in one shell pipe

Sat, 18 Jul 2026 00:00:00 +0000

When you just want to read an API response and don’t feel like installing anything:

bash

curl -s https://api.example.com/thing | python -m json.tool

python -m json.tool ships with every Python install and pretty-prints stdin. No jq, no dependencies. Here’s the whole thing, command and output:

bash

$ echo '{"name":"ada","langs":["go","rust"]}' | python -m json.tool
{
    "name": "ada",
    "langs": [
        "go",
        "rust"
    ]
}

For anything more than eyeballing — filtering, reshaping — reach for jq. For a quick look, this is already on your machine.

git switch beats git checkout

Thu, 09 Jul 2026 00:00:00 +0000

git checkout does too much: it moves branches, restores files, detaches HEAD, and creates branches — all under one overloaded verb. That’s why it’s a classic source of “I ran the right command and lost my changes.”

Since Git 2.23 the job is split into two honest commands:

git switch -c new-feature   # create and move to a branch
git switch main             # move to an existing branch
git restore path/to/file    # discard changes to a file

switch only changes branches. restore only touches files. The name tells you the blast radius before you hit enter.

git commit --fixup and autosquash

Thu, 02 Jul 2026 00:00:00 +0000

When review feedback belongs in a commit three back, you don’t have to hand-edit a rebase todo. Mark the fix, then let Git sort it:

git commit --fixup=<sha>          # stages a "fixup! <subject>" commit
git rebase -i --autosquash main   # reorders and squashes it automatically

--fixup writes a specially-named commit; --autosquash recognizes the name, moves it next to its target, and pre-marks it as fixup in the todo list. You just confirm. Set git config --global rebase.autosquash true and the flag is on by default.

Go's errors.Join

Sat, 27 Jun 2026 00:00:00 +0000

Before Go 1.20, returning “here is everything that’s wrong” meant building your own error slice type. Now the standard library does it:

func validate(u User) error {
    var errs error
    if u.Name == "" {
        errs = errors.Join(errs, errors.New("name is required"))
    }
    if u.Age < 0 {
        errs = errors.Join(errs, errors.New("age must be non-negative"))
    }
    return errs // nil if nothing was joined
}

errors.Join ignores nil arguments, so the accumulate-in-a-loop pattern just works. And errors.Is / errors.As still see through the joined result to each underlying error.

Go's defer runs in LIFO order

Thu, 18 Jun 2026 00:00:00 +0000

Multiple defer statements in a function run in reverse order — the last one deferred runs first:

func process() {
    f := open()
    defer f.Close()      // runs second

    tx := f.Begin()
    defer tx.Rollback()  // runs first
    // ...
}

This is the right default: teardown happens in the reverse of setup, so inner resources release before the outer ones they depend on. It mirrors how a stack unwinds — which is the whole point.