The environment variables the `gem` command and the RubyGems runtime respond to. None of these are required. They override defaults per shell or per process, which makes them useful in CI, in version manager hooks, and for one-off experiments. Persistent preferences belong in a gemrc file instead. See [Configuration](/configuration). ## Paths | Variable | Description | |----------|-------------| | `GEM_HOME` | The directory gems are installed into. See [Where gems are installed and how they load](/gem-installation-and-loading). | | `GEM_PATH` | Directories searched for installed gems, separated by `:` on Unix and `;` on Windows. | | `GEM_SPEC_CACHE` | The directory where gem specifications fetched from remote sources are cached. Defaults to `~/.gem/specs`, or to `$XDG_CACHE_HOME/gem/specs` when `~/.gem/specs` does not exist. | | `GEMRC` | Additional gemrc files to read, separated by `:` on Unix and `;` on Windows. See [Configuration](/configuration). | ## Loading gems | Variable | Description | |----------|-------------| | `RUBYGEMS_GEMDEPS` | Path to a gem dependencies file (`Gemfile`, `gem.deps.rb`, or `Isolate`) whose gems RubyGems activates automatically at startup. The special value `-` searches the current directory and its parents for one. Automatic discovery can execute code from a directory you do not control, so avoid `-` on multiuser systems. | | `GEM_REQUIREMENT_` | A version requirement applied when RubyGems activates the gem ``, uppercased. For example, `GEM_REQUIREMENT_BUNDLER="~> 2.7"` restricts which Bundler version is activated. | ## Building and pushing gems | Variable | Description | |----------|-------------| | `SOURCE_DATE_EPOCH` | A Unix timestamp used instead of the current time when packaging a gem, so that building the same input twice produces byte-identical `.gem` files. | | `RUBYGEMS_HOST` | The gem server that `gem push` sends gems to when no `--host` is given. | | `GEM_HOST_API_KEY` | An API key used to authenticate against the gem server instead of the key stored in `~/.gem/credentials`. | | `GEM_HOST_OTP_CODE` | A one-time password for pushing when the account has multi-factor authentication enabled. Equivalent to `--otp`. | | `GEM_PRIVATE_KEY_PASSPHRASE` | The passphrase of the private signing key, read by `gem cert` and when building signed gems instead of prompting for it. | ## Network | Variable | Description | |----------|-------------| | `HTTP_PROXY`, `HTTP_PROXY_USER`, `HTTP_PROXY_PASS` | The proxy server, and credentials for it, used for connections to gem servers. | | `NO_PROXY` | Hosts that are connected to directly, bypassing the proxy. | ## Other | Variable | Description | |----------|-------------| | `RUBYGEMS_PREVENT_UPDATE_SUGGESTION` | When set, the gem command never suggests running `gem update --system` after noticing a newer RubyGems release. | ## Bundler Bundler variables are not listed here. Every setting understood by `bundle config` can also be set through a corresponding `BUNDLE_*` environment variable, for example `BUNDLE_PATH` or `BUNDLE_WITHOUT`. See [bundle config](/command-reference/bundle-config/).