Function replaceEnvVars

caddyconfig/caddyfile/parse.go:69–111

replaceEnvVars replaces all occurrences of environment variables. It mutates the underlying array and returns the updated slice.

(input []byte)

// replaceEnvVars replaces all occurrences of environment variables.
// It mutates the underlying array and returns the updated slice.
func replaceEnvVars(input []byte) []byte {
	var offset int
	for {
		begin := bytes.Index(input[offset:], spanOpen)
		if begin < 0 {
			break
		}
		begin += offset // make beginning relative to input, not offset
		end := bytes.Index(input[begin+len(spanOpen):], spanClose)
		if end < 0 {
			break
		}
		end += begin + len(spanOpen) // make end relative to input, not begin

		// get the name; if there is no name, skip it
		envString := input[begin+len(spanOpen) : end]
		if len(envString) == 0 {
			offset = end + len(spanClose)
			continue
		}

		// split the string into a key and an optional default
		envParts := strings.SplitN(string(envString), envVarDefaultDelimiter, 2)

		// do a lookup for the env var, replace with the default if not found
		envVarValue, found := os.LookupEnv(envParts[0])
		if !found && len(envParts) == 2 {
			envVarValue = envParts[1]
		}

		// get the value of the environment variable
		// note that this causes one-level deep chaining
		envVarBytes := []byte(envVarValue)

		// splice in the value
		input = append(input[:begin],
			append(envVarBytes, input[end+len(spanClose):]...)...)

		// continue at the end of the replacement
		offset = begin + len(envVarBytes)
	}
	return input
}

type parser struct {
	*Dispenser