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139 lines
2.7 KiB
Markdown
139 lines
2.7 KiB
Markdown
# Env Variable Operators
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These operators are used to handle environment variables usage in expressions and documents. While environment variables can, of course, be passed in via your CLI with string interpolation, this often comes with complex quote escaping and can be tricky to write and read.
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There are three operators:
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- `env` which takes a single environment variable name and parse the variable as a yaml node (be it a map, array, string, number of boolean)
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- `strenv` which also takes a single environment variable name, and always parses the variable as a string.
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- `envsubst` which you pipe strings into and it interpolates environment variables in strings using [envsubst](https://github.com/a8m/envsubst).
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## Tip
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To replace environment variables across all values in a document, `envsubst` can be used with the recursive descent operator
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as follows:
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```bash
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yq eval '(.. | select(tag == "!!str")) |= envsubst' file.yaml
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```
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## Read string environment variable
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Running
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```bash
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myenv="cat meow" yq eval --null-input '.a = env(myenv)'
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```
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will output
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```yaml
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a: cat meow
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```
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## Read boolean environment variable
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Running
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```bash
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myenv="true" yq eval --null-input '.a = env(myenv)'
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```
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will output
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```yaml
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a: true
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```
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## Read numeric environment variable
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Running
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```bash
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myenv="12" yq eval --null-input '.a = env(myenv)'
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```
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will output
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```yaml
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a: 12
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```
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## Read yaml environment variable
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Running
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```bash
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myenv="{b: fish}" yq eval --null-input '.a = env(myenv)'
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```
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will output
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```yaml
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a: {b: fish}
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```
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## Read boolean environment variable as a string
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Running
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```bash
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myenv="true" yq eval --null-input '.a = strenv(myenv)'
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```
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will output
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```yaml
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a: "true"
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```
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## Read numeric environment variable as a string
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Running
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```bash
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myenv="12" yq eval --null-input '.a = strenv(myenv)'
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```
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will output
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```yaml
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a: "12"
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```
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## Dynamic key lookup with environment variable
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Given a sample.yml file of:
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```yaml
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cat: meow
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dog: woof
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```
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then
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```bash
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myenv="cat" yq eval '.[env(myenv)]' sample.yml
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```
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will output
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```yaml
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meow
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```
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## Replace strings with envsubst
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Running
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```bash
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myenv="cat" yq eval --null-input '"the ${myenv} meows" | envsubst'
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```
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will output
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```yaml
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the cat meows
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```
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## Replace strings with envsubst, missing variables
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Running
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```bash
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myenv="cat" yq eval --null-input '"the ${myenvnonexisting} meows" | envsubst'
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```
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will output
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```yaml
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the meows
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```
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## Replace strings with envsubst, missing variables with defaults
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Running
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```bash
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myenv="cat" yq eval --null-input '"the ${myenvnonexisting-dog} meows" | envsubst'
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```
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will output
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```yaml
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the dog meows
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```
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## Replace string environment variable in document
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Given a sample.yml file of:
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```yaml
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v: ${myenv}
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```
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then
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```bash
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myenv="cat meow" yq eval '.v |= envsubst' sample.yml
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```
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will output
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```yaml
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v: cat meow
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```
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