gotwc

README

twc.go - simple world clock in Go 🦦

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

$ twc -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, 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, lighweight (1555 bytes, 67 lines).

Getting Started

Setup

Clone the repository:

git clone https://github.com/Neved4/twc

Build:

$ go build twc.go

Usage

Usage of ./twc:
  -f string
    	Specify file path (default "tz-small.conf")
  -h	Print human-readable format
  -s string
    	Specify time format
  -t string
    	Specify timezone directly

Examples:
    $ twc -h -s %Y-%m-%d -t Asia/Tokyo
        2006-01-02

    $ TZ=America/Los_Angeles twz
        2006-01-02T15:04:05-0800

Environment:
    TZ  Timezone to use when displaying dates.

See also:
    environ(7)

Compatibility

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

License

twc is licensed under the terms of the MIT License.

See the LICENSE file for details.

[^1]: cfr. date command that takes ≈ 931 ms for ≈ 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/IEC 9899:2023: Standard for Information Technology — Programming languages — C, ISO/IEC 9899:2023.
URL: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3096.pdf