murex Shell Docs

Command Reference: mtac

Reverse the order of an array

Description

mtac takes input from STDIN and reverses the order of it.

It’s name is derived from a program called tac - a tool that functions like cat but returns the contents in the reverse order. The difference with the mtac builtin is that it is data-type aware. So it doesn’t just function as a replacement for tac but it also works on JSON arrays, s-expressions, and any other data-type supporting arrays compiled into murex.

Usage

<stdin> -> mtac -> <stdout>

Examples

» ja: [Monday..Friday] -> mtac
[
    "Friday",
    "Thursday",
    "Wednesday",
    "Tuesday",
    "Monday"
]

# Normal output (without mtac)
» ja: [Monday..Friday]
[
    "Monday",
    "Tuesday",
    "Wednesday",
    "Thursday",
    "Friday"
]

Detail

Please bare in mind that while murex is optimised with concurrency and streaming in mind, it’s impossible to reverse an incomplete array. Thus all all of STDIN must have been read and that file closed before mtac can output.

In practical terms you shouldn’t notice any difference except for when STDIN is a long running process or non-standard stream (eg network pipe).

Synonyms

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 Thu Oct 13 08:08:18 UTC 2022 against commit ed6b6fced6b6fc609f4be93c5d3348695a762facfecf48f.

Current version is 2.11.2200 which has been verified against 16798 tests cases.