In Redis, the GETRANGE command allows us to get part of a string at a given key, starting and ending at the specified offsets.

The GETRANGE command replaced the SUBSTR command, which basically does the same thing. The SUBSTR command is now considered deprecated (as of Redis 2.0.0).

Syntax

The syntax for GETRANGE goes like this:

GETRANGE key start end

Example

Suppose we set a key to the following value:

SET band "Avenged Sevenfold"

Result:

OK

And we confirm that it holds that value:

GET band

Result:

"Avenged Sevenfold"

Let’s now use GETRANGE to get part of that value:

GETRANGE band 8 12

Result:

"Seven"

Here, we returned a substring starting at position 8 and ending at position 12.

Negative Offsets

It’s possible to use negative offsets. When doing this, it starts from the end of the string:

GETRANGE band -8 12

Result:

"even"

Note that the second offset value (the end position) specifies the actual position of the end of the string (not the length of the string). To further illustrate this, here’s what happens when the second value is lower than the starting position:

GETRANGE band -8 7

Result:

""

Bear in mind that the second offset value can also be a negative value:

GETRANGE band -8 -5

Result:

"even"

In this case it counts back from the end of the string (just like the starting value did).

When the Offset is Larger than the Original String

The function limits the resulting range to the actual length of the string.

So here’s an example of what happens when the offset values represent a longer string than the original value:

GETRANGE band 8 30

Result:

"Sevenfold"

And here’s what happens when the starting position is outside of the string:

GETRANGE band 20 30

Result:

""

Non Existent Keys

Specifying a non-existent key results in the empty string:

GETRANGE artist 10 12

Result:

""

Wrong Number of Arguments

Specifying no arguments or the wrong number of arguments results in an error:

GETRANGE band 8

Result:

(error) ERR wrong number of arguments for 'getrange' command