Dynamic variables

Dynamic variables (interpolations) are useful when you have a custom configuration data between build environments. For examples, extra build_flags or project dependencies lib_deps.

Each variable should have a next format: ${<section>.<option>}, where <section> is a value from [<section>] group, and <option> is a first item from pair <option> = value.

You can inject system environment variable using sysenv as a section. For example, ${sysenv.HOME}.

  • Variable can be applied only for the option’s value
  • Multiple variables are allowed
  • The Section [platformio] and Section [env] sections are reserved and could not be used as a custom section. Some good section names might be extra or custom.


If you need to share common configuration options between build environments, please take a look at “Global scope” in Section [env] or extends option which allows extending of other sections.


; Unix
lib_extra_dirs = ${sysenv.HOME}/Documents/Arduino/libraries
; Windows
lib_extra_dirs = ${sysenv.HOMEDRIVE}${sysenv.HOMEPATH}\Documents\Arduino\libraries

; You MUST inject these options into [env:] section
; using ${extra.***} (see below)
build_flags = -D VERSION=1.2.3 -D DEBUG=1
lib_deps_builtin =
lib_deps_external = [email protected]>5.6.0

platform = atmelavr
framework = arduino
board = uno
build_flags = ${extra.build_flags}
lib_deps =

platform = espressif8266
framework = arduino
board = nodemcuv2
build_flags = ${extra.build_flags} -DSSID_NAME=HELLO -DSSID_PASWORD=WORLD
lib_deps =
  [email protected]

extends = env:nodemcuv2
platform = espressif32
board = esp32dev