module ENV

ENV is a hash-like accessor for environment variables.

Example

# Set env var PORT to a default if not already set
ENV["PORT"] ||= "5000"
# Later use that env var.
puts ENV["PORT"].to_i

Note

All keys and values are strings. You must take care to cast other types at runtime, e.g. integer port numbers.

Extended modules

Enumerable

Class methods

.[](key : String) : String

Retrieves the value for environment variable named key as a String. Raises KeyError if the named variable does not exist.

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.[]=(key : String, value : String?)

Sets the value for environment variable named key as value. Overwrites existing environment variable if already present. Returns value if successful, otherwise raises an exception. If value is nil, the environment variable is deleted.

If key or value contains a null-byte an ArgumentError is raised.

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.[]?(key : String) : String?

Retrieves the value for environment variable named key as a String?. Returns nil if the named variable does not exist.

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.clear

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.delete(key : String) : String?

Removes the environment variable named key. Returns the previous value if the environment variable existed, otherwise returns nil.

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.each

Iterates over all KEY=VALUE pairs of environment variables, yielding both the key and value.

ENV.each do |key, value|
  puts "#{key} => #{value}"
end

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.fetch(key, default)

Retrieves a value corresponding to the given key. Return the second argument's value if the key does not exist.

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.fetch(key) : String

Retrieves a value corresponding to the given key. Raises a KeyError exception if the key does not exist.

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.fetch(key : String, &block : String -> String?)

Retrieves a value corresponding to a given key. Return the value of the block if the key does not exist.

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.has_key?(key : String) : Bool

Returns true if the environment variable named key exists and false if it doesn't.

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.inspect(io)

Writes the contents of the environment to io.

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.keys : Array(String)

Returns an array of all the environment variable names.

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.pretty_print(pp)

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.values : Array(String)

Returns an array of all the environment variable values.

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