github.com/joomcode/cue@v0.4.4-0.20221111115225-539fe3512047/README.md (about) 1 <!-- 2 Copyright 2018 The CUE Authors 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 --> 16 [](https://pkg.go.dev/github.com/joomcode/cue) 17 [](https://github.com/cue-lang/cue/actions) 18 [](https://golangci.com/r/github.com/cue-lang/cue) 19 [](https://golang.org/dl/) 20 []() 21 22 # The CUE Data Constraint Language 23 24 _Configure, Unify, Execute_ 25 26 CUE is an open source data constraint language which aims 27 to simplify tasks involving defining and using data. 28 29 It is a superset of JSON, 30 allowing users familiar with JSON to get started quickly. 31 32 33 ### What is it for? 34 35 You can use CUE to 36 37 - define a detailed validation schema for your data (manually or automatically from data) 38 - reduce boilerplate in your data (manually or automatically from schema) 39 - extract a schema from code 40 - generate type definitions and validation code 41 - merge JSON in a principled way 42 - define and run declarative scripts 43 44 45 ### How? 46 47 CUE merges the notion of schema and data. 48 The same CUE definition can simultaneously be used for validating data 49 and act as a template to reduce boilerplate. 50 Schema definition is enriched with fine-grained value definitions 51 and default values. 52 At the same time, 53 data can be simplified by removing values implied by such detailed definitions. 54 The merging of these two concepts enables 55 many tasks to be handled in a principled way. 56 57 58 Constraints provide a simple and well-defined, yet powerful, alternative 59 to inheritance, 60 a common source of complexity with configuration languages. 61 62 63 ### CUE Scripting 64 65 The CUE scripting layer defines declarative scripting, expressed in CUE, 66 on top of data. 67 This solves three problems: 68 working around the closedness of CUE definitions (we say CUE is hermetic), 69 providing an easy way to share common scripts and workflows for using data, 70 and giving CUE the knowledge of how data is used to optimize validation. 71 72 There are many tools that interpret data or use a specialized language for 73 a specific domain (Kustomize, Ksonnet). 74 This solves dealing with data on one level, but the problem it solves may repeat 75 itself at a higher level when integrating other systems in a workflow. 76 CUE scripting is generic and allows users to define any workflow. 77 78 79 ### Tooling 80 81 CUE is designed for automation. 82 Some aspects of this are: 83 84 - convert existing YAML and JSON 85 - automatically simplify configurations 86 - rich APIs designed for automated tooling 87 - formatter 88 - arbitrary-precision arithmetic 89 - generate CUE templates from source code 90 - generate source code from CUE definitions (TODO) 91 92 93 ### Download and Install 94 95 #### Release builds 96 97 [Download](https://github.com/cue-lang/cue/releases) the latest release from GitHub. 98 99 #### Install using Homebrew 100 101 Using [Homebrew](https://brew.sh), you can install using the CUE Homebrew tap: 102 103 ``` 104 brew install cue-lang/tap/cue 105 ``` 106 107 #### Install from Source 108 109 <!-- Keep the following in sync with cmd/cue/cmd/testdata/script/install*.txt --> 110 111 If you already have Go 1.16 or later installed, the short version is: 112 113 ``` 114 go install github.com/joomcode/cue/cmd/cue@latest 115 ``` 116 117 This will install the `cue` command line tool. 118 119 For more details see [Installing CUE](./doc/install.md). 120 121 122 ### Learning CUE 123 124 The fastest way to learn the basics is to follow the 125 [tutorial on basic language constructs](./doc/tutorial/basics/Readme.md). 126 127 A more elaborate tutorial demonstrating of how to convert and restructure 128 an existing set of Kubernetes configurations is available in 129 [written form](./doc/tutorial/kubernetes/README.md). 130 131 ### References 132 133 - [Language Specification](./doc/ref/spec.md): official CUE Language specification. 134 135 - [API](https://pkg.go.dev/github.com/joomcode/cue/cue): the API on pkg.go.dev 136 137 - [Builtin packages](https://pkg.go.dev/github.com/joomcode/cue/pkg): builtins available from CUE programs 138 139 - [`cue` Command line reference](./doc/cmd/cue.md): the `cue` command 140 141 142 ### Contributing 143 144 Our canonical Git repository is located at 145 https://review.gerrithub.io/q/project:cue-lang%252Fcue. 146 147 To contribute, please read the [Contribution Guide](./doc/contribute.md). 148 149 To report issues or make a feature request, use the 150 [issue tracker](https://cuelang.org/issues). 151 152 Changes can be contributed using Gerrit or Github pull requests. 153 154 155 ## Code of Conduct 156 157 Guidelines for participating in CUE community spaces and a reporting process for 158 handling issues can be found in the [Code of 159 Conduct](https://cuelang.org/docs/contribution_guidelines/conduct). 160 161 162 ## Contact 163 164 You can get in touch with the cuelang community in the following ways: 165 166 - Ask questions via [GitHub Discussions](https://github.com/cue-lang/cue/discussions) 167 - Chat with us on our 168 [Slack workspace](https://join.slack.com/t/cuelang/shared_invite/enQtNzQwODc3NzYzNTA0LTAxNWQwZGU2YWFiOWFiOWQ4MjVjNGQ2ZTNlMmIxODc4MDVjMDg5YmIyOTMyMjQ2MTkzMTU5ZjA1OGE0OGE1NmE). 169 170 --- 171 172 Unless otherwise noted, the CUE source files are distributed 173 under the Apache 2.0 license found in the LICENSE file. 174 175 This is not an officially supported Google product. 176