c-duration

A small single-header library to parse and format durations. Available in both C (duration.h) and C++ (duration.hpp).

Features

• Parse compact duration strings like 1h30m.
• Parse decimal values (dot or comma) and flexible unit names like 1.5 hrs, 2,5minutes, 3.5 days.
• Format seconds into compact (1h30m) or human-readable (1 hour 30 minutes) output.
• Simple compile-time configuration for year length.

Supported Units

• s second
• m minute
• h hour
• d day
• w week
• y year (DURATION_YEAR_DAYS, default 365)

Aliases are also accepted:

• seconds: sec, secs, second, seconds
• minutes: min, mins, minute, minutes
• hours: hr, hrs, hour, hours
• days: day, days
• weeks: wk, wks, week, weeks
• years: yr, yrs, year, years

Quick Start

C

#define DURATION_IMPLEMENTATION
#include "duration.h"

#include <stdio.h>

int main(void) {
	char buf[64];
	long seconds = duration_parse("1h30m");

	duration_format(seconds, buf, sizeof(buf), false);
	printf("compact: %s\n", buf); // 1h30m

	duration_format(seconds, buf, sizeof(buf), true);
	printf("human: %s\n", buf);   // 1 hour 30 minutes

	return 0;
}

C++

#include "duration.hpp"
#include <iostream>

int main() {
	long seconds = duration::parse("1h30m");

	std::cout << duration::format(seconds)       << "\n"; // 1h30m
	std::cout << duration::format(seconds, true) << "\n"; // 1 hour 30 minutes
}

The C++ header is fully self-contained — no #define guard needed. All functions are in the duration namespace and return std::string.

API

C (duration.h)

long duration_parse(const char *s);
void duration_format(long seconds, char *buf, int bufsize, bool human_readable);

C++ (duration.hpp)

namespace duration {
    long        parse (std::string_view s);
    std::string format(long seconds, bool human_readable = false);
}

parse / duration_parse

• Returns total seconds parsed from the input string.
• Supports integer and decimal values with . or , (for example: 1.5h, 1,5h, 2.5minutes).
• Parses left-to-right and stops at the first invalid token.
• Example: "1h junk" returns 3600.
• Whitespace between chunks is allowed.
• C version returns 0 when passed NULL.

format / duration_format

• If human_readable is false, output is compact (1h30m).
• If human_readable is true, output uses words and spacing (1 hour 30 minutes).
• If seconds <= 0, returns "0s" (compact) or "0 seconds" (human readable).
• C version: writes into buf; returns immediately if buf == NULL or bufsize <= 0.

Configuration

Override year length before including either header:

#define DURATION_YEAR_DAYS 360

Build and Test

make test      # C only
make test_cpp  # C++ only
make all       # both