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Kenneth Reitz
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2.9 KiB
ReStructuredText
72 lines
2.9 KiB
ReStructuredText
`|Redis Documentation| <index.html>`_
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**ReplyTypes: Contents**
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`Redis Reply Types <#Redis%20Reply%20Types>`_
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`Status code reply <#Status%20code%20reply>`_
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`Error reply <#Error%20reply>`_
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`Integer reply <#Integer%20reply>`_
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`Bulk reply <#Bulk%20reply>`_
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`Multi bulk reply <#Multi%20bulk%20reply>`_
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ReplyTypes
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==========
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Redis Reply Types
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=================
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Redis commands can reply to the client with four different kind of
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replies, you can find the protocol level specification of this
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replies in the
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`Redis Protocol Specification <ProtocolSpecification.html>`_. This
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page is instead an higher level description of the four types of
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replies from the point of view of the final user.
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Status code reply
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=================
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Status code replies are single line strings having the **+**
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character as first byte. The string to return to the client is
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simply verything that follows the first **+** character. For
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example the `PING <PingCommand.html>`_ command returns **+PONG**,
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that is the string "PONG".
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Error reply
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===========
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This is like a status code reply but the first character is **-**
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instead of **+**. The client library should raise an error for
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error replies and stop the execution of the program if the
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exception is not trapped, showing the error message (everything
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following the first **-** character). An example of error is
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"-Error no such key" or "-foobar". Note that error replies will not
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collide with negative integer replies since integer replies are
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prefixed with the **:** character.
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Integer reply
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=============
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At protocol level integer replies are single line replies in form
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of a decimal singed number prefixed by a **:** character. For
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example **:10** is an integer reply. Redis commands returning
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*true* or *false* will use an integer reply with 0 or 1 as values
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where 0 is false and 1 is true.
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Integer replies are usually passed by client libraries as integer
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values.
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Bulk reply
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==========
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A bulk reply is a binary-safe reply that is used to return a binary
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safe single string value (string is not limited to alphanumerical
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strings, it may contain binary data of any kind). Client libraries
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will usually return a string as return value of Redis commands
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returning bulk replies. There is a special bulk reply that signal
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that the element does not exist. When this happens the client
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library should return 'nil', 'false', or some other special element
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that can be distinguished by an empty string.
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Multi bulk reply
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================
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While a bulk reply returns a single string value, multi bulk
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replies are used to return multiple values: lists, sets, and so on.
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Elements of a bulk reply can be missing. Client libraries should
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return 'nil' or 'false' in order to make this elements
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distinguishable from empty strings. Client libraries should return
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multi bulk replies that are about ordered elements like list ranges
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as lists, and bulk replies about sets as hashes or Sets if the
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implementation language has a Set type.
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.. |Redis Documentation| image:: redis.png |