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vendor/github.com/mfridman/interpolate/README.md

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+# Interpolate
+
+[![Build Status](https://github.com/mfridman/interpolate/actions/workflows/ci.yaml/badge.svg)](https://github.com/mfridman/interpolate/actions/workflows/ci.yaml)
+[![Go Reference](https://pkg.go.dev/badge/github.com/mfridman/interpolate.svg)](https://pkg.go.dev/github.com/mfridman/interpolate)
+[![Go Report Card](https://goreportcard.com/badge/github.com/mfridman/interpolate)](https://goreportcard.com/report/github.com/mfridman/interpolate)
+
+A Go library for parameter expansion (like `${NAME}` or `$NAME`) in strings from environment
+variables. An implementation of [POSIX Parameter
+Expansion](http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_02),
+plus some other basic operations that you'd expect in a shell scripting environment [like
+bash](https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html).
+
+## Installation
+
+```
+go get github.com/mfridman/interpolate@latest
+```
+
+## Usage
+
+```go
+package main
+
+import (
+  "github.com/mfridman/interpolate"
+  "fmt"
+)
+
+func main() {
+  env := interpolate.NewSliceEnv([]string{
+    "NAME=James",
+  })
+
+  output, _ := interpolate.Interpolate(env, "Hello... ${NAME} welcome to the ${ANOTHER_VAR:-🏖}")
+
+  fmt.Println(output)
+  // Output: Hello... James welcome to the 🏖
+}
+```
+
+## Supported Expansions
+
+- `${parameter}` or `$parameter`
+
+  - **Use value.** If parameter is set, then it shall be substituted; otherwise, it will be blank
+
+- `${parameter:-[word]}`
+
+  - **Use default values.** If parameter is unset or null, the expansion of word (or an empty string
+    if word is omitted) shall be substituted; otherwise, the value of parameter shall be
+    substituted.
+
+- `${parameter-[word]}`
+
+  - **Use default values when not set.** If parameter is unset, the expansion of word (or an empty
+    string if word is omitted) shall be substituted; otherwise, the value of parameter shall be
+    substituted.
+
+- `${parameter:[offset]}`
+
+  - **Use the substring of parameter after offset.** A negative offset must be separated from the
+    colon with a space, and will select from the end of the string. If the value is out of bounds,
+    an empty string will be substituted.
+
+- `${parameter:[offset]:[length]}`
+
+  - **Use the substring of parameter after offset of given length.** A negative offset must be
+    separated from the colon with a space, and will select from the end of the string. If the offset
+    is out of bounds, an empty string will be substituted. If the length is greater than the length
+    then the entire string will be returned.
+
+- `${parameter:?[word]}`
+  - **Indicate Error if Null or Unset.** If parameter is unset or null, the expansion of word (or a
+    message indicating it is unset if word is omitted) shall be returned as an error.
+
+## Prior work
+
+This repository is a fork of [buildkite/interpolate](https://github.com/buildkite/interpolate). I'd
+like to thank the authors of that library for their work. I've forked it to make some changes that I
+needed for my own use cases, and to make it easier to maintain. I've also added some tests and
+documentation.
+
+## License
+
+Licensed under MIT license, in `LICENSE`.