halo · nim · ~400 loc

ascii progress bars.
one binary.

library and cli in the same file. works in your nim code, works as a pipe in your shell. terminal from stdlib is all it needs. tqdm-ish without pulling in anything.

$ halo --bar 100 -- sh -c 'for i in $(seq 1 100); do sleep 0.02; done'

[███████████▓░░░░░░░░]  55%  55/100  eta 0m01s

library

drop it in nim code.

import halo, std/os

var bar = newBar(total = 1000, width = 40)
for i in 0 ..< 1000:
  bar.update(i + 1, msg = "step " & $i)
  sleep(2)
bar.finish()

var spin = newSpinner(frames = brailleFrames)
spin.start("loading")
doSomeWork()
spin.succeed("done")

bar styles: bsSolid bsDots bsArrows bsBraille bsAscii. spinner frames live in glyphs.nim. the spinner is a ref because it owns a worker thread; succeed / fail / stop joins it and prints one final line.

cli

three ways to use it.

bar around a command

$ halo --bar 100 -- ./longjob

spinner while you wait

$ halo --spin "installing" -- npm install

pass-through pipe counter

$ cat big.csv | halo --pipe --label "parsing" > out

good defaults

non-tty output (pipe, file, ci logs) falls back to plain lines. no escape codes leak.
sigint restores the cursor before exiting. exit code is 130.
NO_COLOR=1 is honored in --color auto.
spinner interval has a 20ms floor so you don't pin a cpu at zero.

threaded spinner is gc:arc-friendly. haven't stress-tested nested spinners, probably don't. windows ansi works in recent terminals. older cmd.exe untested.

install

$ nimble install halo
# or clone and nimble install from the checkout.
# binary drops in ~/.nimble/bin/halo

ascii progress bars.one binary.

drop it in nim code.

three ways to use it.

ascii progress bars.
one binary.