The USER command lets a user set their username and realname while connecting to the server. This command cannot be used after connection registration has completed.
USER <username> 0 * <realname>
<username>: The username to set (i.e. theuserpart of theirnick!user@host).<realname>: The realname (or gecos) to set. May contain spaces.
The <username> submitted is the one the client prefers, but servers may silently modify or truncate it before setting it on the user. The maximum length of the username may be specified by the USERLEN 005 parameter.
Some servers set the username of connecting clients automatically by relying on the Ident Protocol. In these servers, the username retrieved via Ident is preferred over the one submitted by the client. When connecting to these servers, if the submitted <username> is used, it will commonly be prefixed with a tilde (~) to indicate that it’s user-set.
The second and third parameters have different definitions depending on the source you refer to, and the software the server is running. To prevent any unexpected results, we recommend always sending a zero (0) and an asterisk (*) for these parameters.
If a client tries to sent the USER command after connection registration has been completed, the ERR_ALREADYREGISTRED reply is sent and the command is ignored.
Examples
C1 -> nick alice
C1 -> user ali 0 * :My name is
S1 <- :irc.example.com 001 alice :Welcome to the ExampleNet Internet Relay Chat Network alice
S1 <- <connection burst>
C1 -> PRIVMSG ben :What's the password?
S2 <- :alice!~ali@localhost PRIVMSG ben :What's the password?
Setting username, and username as seen by another user
C1 -> nick alice
C1 -> user ali 0 * :My name is
S1 <- :irc.example.com 001 alice :Welcome to the ExampleNet Internet Relay Chat Network alice
S1 <- <connection burst>
C1 -> PRIVMSG ben :What's the password?
S2 <- :alice!uid21341@localhost PRIVMSG ben :What's the password?
Username retrieved with Ident, as seen by another user
C -> USER ger 0 * :I want to change my gecos!
S <- :irc.example.com 462 alice :You may not reregister
Attempting USER after connection registration has completed
C -> NICK alice
C -> USER ali 0 *
S <- :irc.example.com 461 alice USER :Not enough parameters
USER with no <realname> parameter
Compatibility
Related Numerics
ERR_NEEDMOREPARAMS (461)ERR_ALREADYREGISTRED (462)
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