23/Flux Standard Duration

This specification describes a simple string format used to represent a duration of time.


The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.


Many Flux utilities and services may take a time duration as input either via user-provided options, configuration input, or message payload contents. To provide a consistent interface, and reduce the chance of incompatibility between Flux components, it is useful to standardize on a duration format that is human readable, easily parsed, and compact.

Utilities and services that support the duration form described here are said to support “Flux Standard Duration.”


A duration in Flux Standard Duration SHALL be of the form N[SUFFIX] where SUFFIX SHALL be optional and, if provided, MUST be a string from the set { ms, s, m, h, d }. The value N MUST be a non-negative, non-infinite, floating-point number excluding NaN. The value N SHALL be in one of the forms allowed by C99 1 strtof or strtod and SHALL be interpreted as:

  • milliseconds if SUFFIX is ms.

  • seconds if SUFFIX is not provided, or is s.

  • minutes if SUFFIX is m.

  • hours if SUFFIX is h.

  • days if SUFFIX is d.


C99 - ISO/IEC 9899:1999 standard section The strtod, strtof, and strtold functions