I thought I’d compile a list of Redis commands that can be used to set strings. Each command has its own specific use, and so the command used will depend on the situation.

In any case, here are 14 commands that set strings in Redis.

The SET Command

The SET command sets a given key to a specific string value:

SET animal "Cat"

Result:

OK

This command returns OK when the value is successfully set.

The SET command also accepts a bunch of optional arguments that allow us to do more than just set the string. For example, there are arguments that allow us to set the expiry of the key. And there’s also a GET option that enables us to return the old string that was stored at the key before we set it to the new value.

Here’s an example of using the GET option when setting the key to a different value:

SET animal "Dog" GET

Result:

"Cat"

In this case, I set the key to Dog and returned the old value (which is Cat).

We can check the new value with the GET command:

GET animal

Result:

"Dog"

The key now contains Dog as expected.

The SETNX Command

The SETNX command is similar to SET, except that it only sets the key if it doesn’t already exist.

Here’s an example of setting a key that doesn’t already exist:

SETNX country "Mexico"

Result:

(integer) 1

The integer reply of 1 indicates that the key was successfully set (it didn’t previously exist).

Here’s what happens if we try to set the key again:

SETNX country "Sweden"

Result:

(integer) 0

This time we get an integer reply of 0, which means that the key wasn’t set. That’s because it already exists.

The MSET Command

The MSET command allows us to set multiple keys:

MSET animal "Bird" plant "Tree"

Result:

OK

In this case I set the animal key and the plant key.

There’s also an MGET command that allows us to return the value of multiple keys. Let’s use it now to check our keys:

MGET animal plant

Result:

1) "Bird"
2) "Tree"

Exactly as expected.

The MSETNX Command

Redis also has an MSETNX command, which sets the keys only if none of them already exist:

MSETNX animal "Zebra" color "Blue"

Result:

(integer) 0

In the above example, the color key doesn’t exist but the animal key does, therefore nothing was set.

Let’s change the first key to one that doesn’t exist:

MSETNX pet "Zebra" color "Blue"

Result:

(integer) 1

This time all keys were set. We know this because we got an integer reply of 1.

The SETEX Command

The SETEX command sets a key and its expiry in seconds:

SETEX animal 60 "Buffalo"

Result:

OK

Here, I set the key to Buffalo, with an expiry of 60 seconds. This means that the key will no longer exist after 60 seconds (unless it’s reset or its expiry is changed).

The PSETEX Command

The PSETEX command is similar to SETEX, except that the expiry is in milliseconds:

SETEX animal 60000 "Antelope"

Result:

OK

Here, I set the key to Antelope, with an expiry of 60000 milliseconds. The key will no longer exist after 60000 seconds (unless it’s reset or its expiry is changed).

The INCR Command

The INCR command increments a value stored at a given key by one:

INCR counter

Result:

(integer) 1

If the key doesn’t exist, it’s created with a value of 0, then incremented by 1. This is what happened in my example above, and we can see this with the integer reply of 1.

Let’s run the code again:

INCR counter

Result:

(integer) 2

Now we get an integer reply of 2, which is the key’s current value.

The INCRBY Command

The INCRBY command increments a value stored at a given key by the specified amount:

INCRBY counter 10

Result:

(integer) 12

Here, I incremented the existing value by 10, so the key now holds a value of 12.

The INCRBYFLOAT Command

The INCRBYFLOAT command increments a value stored at a given key by the specified floating point number:

INCRBYFLOAT counter 2.57

Result:

14.57

Here, I incremented the existing value by 2.57, so the key now holds a value of 14.57.

The DECR Command

The DECR command decrements a value stored at a given key by one:

DECR points

Result:

(integer) -1

Here, I decremented a key that didn’t exist. Therefore, it was created, set to zero, and decremented by one.

Let’s decrement it again:

DECR points

Result:

(integer) -2

The DECRBY Command

The DECRBY command decrements a value stored at a given key by the specified amount:

DECRBY points 10

Result:

(integer) -12

The APPEND Command

The APPEND command appends the specified value to the end of a string. If the key doesn’t exist, it is created with the value:

APPEND colors "Blue"

Result:

(integer) 4

This command returns the length of the string after the append operation. In my case, the key didn’t exist and so it was created with the specified value. The value is four characters long, and so I get an integer reply of 4.

The SETRANGE Command

The SETRANGE command overwrites part of the string stored at the specified key. However, if the key doesn’t exist, it’s created with the specified value:

SETRANGE countries 0 "Belize"

Result:

(integer) 6

This command returns an integer reply of the length of the string after the operation has been applied. In my case, the key didn’t exist and so it was created with the specified value. Therefore, the string’s length matches that of the value that I set.

The GETSET Command

I was hesitant to include this command, because it is now deprecated (due to the SET command being able to provide the same functionality). But here it is anyway.

The GETSET command does the same thing that we did previously with the GET option of the SET command – it sets a given key and returns its old value:

GETSET animal "Bird"

Result:

"Dog"

So this time I set the key to Bird and it returned its old value of Dog.

Let’s check the key’s current value:

GET animal

Result:

"Bird"

Exactly as expected.

As alluded to, it’s best to avoid this command due to it being deprecated. Better to use the SET command with the GET option.