ymask

NAME

ymask - Mask a data structure to display only the desired fields

SYNOPSIS

    ymask <mask> [<file>...]

    ymask -h|--help|--version

DESCRIPTION

This program takes a stream of YAML documents (on STDIN or file arguments), and prints only the fields specified by the mask.

ARGUMENTS

mask

See MASK SYNTAX for more information

<file>

A YAML file to read. The special file "-" refers to STDIN. If no files are specified, read STDIN.

OPTIONS

-h | --help

Show this help document.

--version

Print the current ymask and Perl versions.

MASK SYNTAX

PROPERTIES

    $ ymask 'name,rank,serial'

Select multiple properties in a document using ,. If a property does not exist, nothing will be added (and no error or warning will be output).

DESCENDANTS

    $ ymask 'squad/name'

Select an inner document's properties using /. Arrays are automatically looped over.

SUB-SELECTION

    $ ymask 'squad(name,location)'

Select multiple parts of an inner document by using parentheses.

WILDCARDS

    $ ymask 'squad/*/city'

Select every property in a document, which is useful for picking parts out of every inner document.

EXAMPLES

All these examples use the following documents:

    ---
    name: Hazel Murphy
    role: Captain
    nickname: Hank
    history:
        - location: Sealab
          from: 2014-01-01
        - location: USS Hunley
          from: 2012-06-01
          to: 2013-11-28
    ---
    name: Quinn Quinlan
    role: Science Officer
    nickname: Doctor
    history:
        - location: Sealab
          from: 2014-04-01
        - location: MIT
          from: 2008-08-01
          to: 2012-06-05
    ---
    name: Debbie Dupree
    role: Oceanographer
    history:
        - location: Sealab
          from: 2014-02-10
        - location: Sea Parks
          from: 2004-09-01
          to: 2014-01-20

SELECT MULTIPLE PROPERTIES

    $ ymask 'name,role,nickname'
    ---
    name: Hazel Murphy
    nickname: Hank
    role: Captain
    ---
    name: Quinn Quinlan
    nickname: Doctor
    role: Science Officer
    ---
    name: Debbie Dupree
    role: Oceanographer

SELECT PROPERTIES IN ARRAYS

    $ ymask 'name,history/location'
    ---
    history:
      - location: Sealab
      - location: USS Hunley
    name: Hazel Murphy
    ---
    history:
      - location: Sealab
      - location: MIT
    name: Quinn Quinlan
    ---
    history:
      - location: Sealab
      - location: Sea Parks
    name: Debbie Dupree

ENVIRONMENT VARIABLES

YERTL_FORMAT: Specify the default format Yertl uses between commands. Defaults to yaml. Can be set to json for interoperability with other programs.