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layout: default
title: Fig environment variables reference
---
Environment variables reference
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Fig uses [Docker links] to expose services' containers to one another. Each linked container injects a set of environment variables, each of which begins with the uppercase name of the container.
To see what environment variables are available to a service, run `fig run SERVICE env`.
name\_PORT
Full URL, e.g. `DB_1_PORT=tcp://172.17.0.5:5432`
name\_PORT\_num\_protocol
Full URL, e.g. `DB_1_PORT_5432_TCP=tcp://172.17.0.5:5432`
name\_PORT\_num\_protocol\_ADDR
Container's IP address, e.g. `DB_1_PORT_5432_TCP_ADDR=172.17.0.5`
name\_PORT\_num\_protocol\_PORT
Exposed port number, e.g. `DB_1_PORT_5432_TCP_PORT=5432`
name\_PORT\_num\_protocol\_PROTO
Protocol (tcp or udp), e.g. `DB_1_PORT_5432_TCP_PROTO=tcp`
name\_NAME
Fully qualified container name, e.g. `DB_1_NAME=/myapp_web_1/myapp_db_1`
[Docker links]: http://docs.docker.io/en/latest/use/port_redirection/#linking-a-container