murex Shell Docs

API Reference: ReadIndex() (type)

Data type handler for the index, [, builtin


This is a function you would write when programming a murex data-type.

It's called by the index, [, builtin.

The purpose of this function is to allow builtins to support sequential reads (where possible) and also create a standard interface for [ (index), thus allowing it to be data-type agnostic.


Registering your ReadIndex()

// To avoid data races, this should only happen inside func init()
lang.ReadIndexes[ /* your type name */ ] = /* your readIndex func */


Example ReadIndex() function:

package json

import (

func index(p *lang.Process, params []string) error {
    var jInterface interface{}

    b, err := p.Stdin.ReadAll()
    if err != nil {
        return err

    err = json.Unmarshal(b, &jInterface)
    if err != nil {
        return err

    marshaller := func(iface interface{}) ([]byte, error) {
        return json.Marshal(iface, p.Stdout.IsTTY())

    return lang.IndexTemplateObject(p, params, &jInterface, marshaller)


While there is support for a dedicated ReadNotIndex() for instances of ![, the template APIs lang.IndexTemplateObject and lang.IndexTemplateTable are both agnostic to the bang prefix.


  1. *lang.Process: Process's runtime state. Typically expressed as the variable p
  2. []string: slice of parameters used in [

See Also

This site's content is rebuilt automatically from murex's source code after each merge to the master branch. Downloadable murex binaries are also built with the website.

Last built on Tue Jun 22 08:18:17 UTC 2021 against commit 2235c7b2235c7b18f86f1cf214e246b88b0ea193d87fe80.

Current version is 2.2.1100 BETA which has been verified against tests.