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Go CodeQL Homebrew

gotwc - Tiny world clock in Go! 🚀

Fast, CLI world clock that displays time zone information using tz database to read valid tz entries.

$ gotwc -h -f tools/samples/tz-small.conf
America/New_York     2023-12-11 12:37:13
America/Los_Angeles  2023-12-11 09:37:13
UTC                  2023-12-11 17:37:13
Europe/London        2023-12-11 17:37:13
Europe/Paris         2023-12-11 18:37:13
Asia/Tokyo           2023-12-12 02:37:13
Australia/Sydney     2023-12-12 04:37:13

Highlights

  • 🚀 Fast - 10X times faster than twc.c and 65X times faster than date.1
    Only ≈ 7 ms for one entry, and ≈ 177 ms for ≈ 600 entries.
  • 🔒 Robust - tested to work with all tz database entries, version 2023c.
  • 📦 Self-contained - zero dependencies, lightweight (110 lines, 2458 bytes).

Getting Started

Setup

If you have Homebrew installed, just run:

$ brew tap Neved4/homebrew-tap/gotwc

Alternatively, clone the repository:

$ git clone https://github.com/Neved4/gotwc

Then build:

$ go build

Usage

The following usage and options are available:

gotwc [-h] [-f path] [-s format] [-t timezone] ...

Options:
  -f path
      Read config from path (default "$HOME/.config/twc/tz.conf")
  -h
      Print in human-readable format
  -s format
      Set desired time format (e.g. "%Y-%m-%d")
  -t timezone
      specific timezone (e.g. "Asia/Tokyo")

Examples:
  Print Tokyo's date in a human-readable format with YY-MM-DD format:

    $ gotwc -h -s %Y-%m-%d -t Asia/Tokyo
    Asia/Tokyo  2024-01-02 15:04:05
  
  Print date in Los Angeles using an environment variable for the timezone:
  
    $ TZ=America/Los_Angeles gotwc
    2024-01-02T15:04:05-0800

Environment:
  XDG_CONFIG_HOME
    When defined, it will be used to store the tz.conf file.
  TZ
    Timezone to use when displaying dates.

Files:
  ~/.config/twc/tz.conf
    Stores tz database entries to be displayed.

See also:
  environ(7)

Docker

To compile the binary inside a Docker image, run:

docker build .

Compatibility

Runs on Linux, macOS and *BSD systems on both x86_64 and arm64.

Standards

gotwc should run on most POSIX.1-20172 compatible systems and produce ISO 86013 output.

License

gotwc is licensed under the terms of the MIT License.

See the LICENSE file for details.

Related Projects

Footnotes

  1. cfr. date command takes ≈ 931 ms when iterating over ≈ 600 entries. Measured with hyperfine. ↩

  2. IEEE Std 1003.1-2017: Standard for Information Technology — Portable Operating System Interface (POSIX®),
    ISO/IEC/IEEE 9945:2009/COR 2:2017. URL: https://pubs.opengroup.org/onlinepubs/9699919799/ ↩

  3. ISO 8601: Date and time \ — Representations for information interchange, ISO 8601-1:2019.
    URL: https://www.iso.org/obp/ui/#iso:std:iso:8601:-2:ed-1:v1:en ↩