Memcached: Replace Data

REPLACE command is used to replace the value of an existing key. If the key don’t exists, then it return ‘NOT_STORED’.

Syntax

replace key flags exptime bytes [noreply] value

Following table summarizes the arguments of replace command.

Argument	Description
key	Name of the key.
flags	It is 32-bit unsigned integer, stored along with the data in the server and retrieved when you get the <key value> pair.
exptime	Expiry time of the data stored in cache. It is represented in seconds.
bytes	length of the data in bytes that needs to be stored in Memcached.
noreply	It is optional, when you pass this parameter, server don’t send any reply back to you.
value	Value to be stored in Memcached server.

Open new terminal and use telnet to connect to memcached server.

telnet <hostname> <port>

By default memcached server listen on port 11211.

$ telnet 127.0.0.1 11211
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
set 1 0 900 11
harikrishna
STORED
get 1
VALUE 1 0 11
harikrishna
END
replace 1 0 900 4
gopi
STORED
get 1
VALUE 1 0 4
gopi
END

Now to try to replace a value, where key don’t exist, you will get error like ‘NOT_STORED’.

get 2
END
replace 2 0 900 4
gopi
NOT_STORED

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