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Env Variable Operators

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.
There are three operators:
  • 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)
  • strenv which also takes a single environment variable name, and always parses the variable as a string.
  • envsubst which you pipe strings into and it interpolates environment variables in strings using envsubst.

EnvSubst Options

You can optionally pass envsubst any of the following options:
  • nu: NoUnset, this will fail if there are any referenced variables that are not set
  • ne: NoEmpty, this will fail if there are any referenced variables that are empty
  • ff: FailFast, this will abort on the first failure (rather than collect all the errors)
E.g: envsubst(ne, ff) will fail on the first empty variable.
See Imposing Restrictions in the envsubst documentation for more information, and below for examples.

Tip

To replace environment variables across all values in a document, envsubst can be used with the recursive descent operator as follows:
yq '(.. | select(tag == "!!str")) |= envsubst' file.yaml

Read string environment variable

Running
myenv="cat meow" yq --null-input '.a = env(myenv)'
will output
a: cat meow

Read boolean environment variable

Running
myenv="true" yq --null-input '.a = env(myenv)'
will output
a: true

Read numeric environment variable

Running
myenv="12" yq --null-input '.a = env(myenv)'
will output
a: 12

Read yaml environment variable

Running
myenv="{b: fish}" yq --null-input '.a = env(myenv)'
will output
a: {b: fish}

Read boolean environment variable as a string

Running
myenv="true" yq --null-input '.a = strenv(myenv)'
will output
a: "true"

Read numeric environment variable as a string

Running
myenv="12" yq --null-input '.a = strenv(myenv)'
will output
a: "12"

Dynamically update a path from an environment variable

The env variable can be any valid yq expression.
Given a sample.yml file of:
a:
b:
- name: dog
- name: cat
then
pathEnv=".a.b[0].name" valueEnv="moo" yq 'eval(strenv(pathEnv)) = strenv(valueEnv)' sample.yml
will output
a:
b:
- name: moo
- name: cat

Dynamic key lookup with environment variable

Given a sample.yml file of:
cat: meow
dog: woof
then
myenv="cat" yq '.[env(myenv)]' sample.yml
will output
meow

Replace strings with envsubst

Running
myenv="cat" yq --null-input '"the ${myenv} meows" | envsubst'
will output
the cat meows

Replace strings with envsubst, missing variables

Running
yq --null-input '"the ${myenvnonexisting} meows" | envsubst'
will output
the meows

Replace strings with envsubst(nu), missing variables

(nu) not unset, will fail if there are unset (missing) variables
Running
yq --null-input '"the ${myenvnonexisting} meows" | envsubst(nu)'
will output
Error: variable ${myenvnonexisting} not set

Replace strings with envsubst(ne), missing variables

(ne) not empty, only validates set variables
Running
yq --null-input '"the ${myenvnonexisting} meows" | envsubst(ne)'
will output
the meows

Replace strings with envsubst(ne), empty variable

(ne) not empty, will fail if a references variable is empty
Running
myenv="" yq --null-input '"the ${myenv} meows" | envsubst(ne)'
will output
Error: variable ${myenv} set but empty

Replace strings with envsubst, missing variables with defaults

Running
yq --null-input '"the ${myenvnonexisting-dog} meows" | envsubst'
will output
the dog meows

Replace strings with envsubst(nu), missing variables with defaults

Having a default specified skips over the missing variable.
Running
yq --null-input '"the ${myenvnonexisting-dog} meows" | envsubst(nu)'
will output
the dog meows

Replace strings with envsubst(ne), missing variables with defaults

Fails, because the variable is explicitly set to blank.
Running
myEmptyEnv="" yq --null-input '"the ${myEmptyEnv-dog} meows" | envsubst(ne)'
will output
Error: variable ${myEmptyEnv} set but empty

Replace string environment variable in document

Given a sample.yml file of:
v: ${myenv}
then
myenv="cat meow" yq '.v |= envsubst' sample.yml
will output
v: cat meow

(Default) Return all envsubst errors

By default, all errors are returned at once.
Running
yq --null-input '"the ${notThere} ${alsoNotThere}" | envsubst(nu)'
will output
Error: variable ${notThere} not set
variable ${alsoNotThere} not set

Fail fast, return the first envsubst error (and abort)

Running
yq --null-input '"the ${notThere} ${alsoNotThere}" | envsubst(nu,ff)'
will output
Error: variable ${notThere} not set
Last modified 30d ago