Irssi is a modular IRC client for UNIX that currently has only text mode user interface, but 80-90% of the code isn't text mode specific, so other UIs could be created pretty easily.
Irssi also isn't really even IRC specific anymore, there's already working SILC and ICB modules available. Support for other protocols like ICQ and Jabber could be created some day too.
Here are some key features of "Irssi":
· There's lots of things Irssi does for you automatically that some people like and others just hate. Things like: nick completion, creating new window for newly joined channel, creating queries when msgs/notices are received or when you send a msg, closing queries when it's been idle for some time, etc.
· I think Irssi has clearly the best support for handling multiple server connections. You can have as many as you want in as many ircnets as you want. Having several connections in one server works too, for example when you hit the (ircnet's) 10 channels/connection limit you can just create another connection and you hardly notice it. If connection to server is lost, Irssi tries to connect back until it's successful. Also channels you were joined before disconnection are restored, even if they're "temporarily unavailable" because of netsplits, Irssi keeps rejoining back to them. Also worth noticing - there's not that stupid "server is bound to this window, if this window gets closed the connection closes" thing that ircII based clients have.
· You can specify what channels to join to immediately after connected to some server or IRC network. After joined to channel, Irssi can automatically request ops for you (or do anything, actually) from channel's bots.
Window content saving:
· Say /LAYOUT SAVE when you've put all the channels and queries to their correct place, and after restarting Irssi, the channels will be joined back into windows where they were saved.
Tab completing anything:
· You can complete lots of things with tab: nicks, commands, command -options, file names, settings, text format names, channels and server names. There's also an excellent /msg completion that works transparently with multiple IRC networks. Completing channel nicks is also pretty intelligent, it first goes through the people who have talked to you recently, then the people who have talked to anyone recently and only then it fallbacks to rest of the nicks. You can also complete a set of words you've specified, for example homepage< tab > changes it to your actual home page URL.
· You can log any way you want and as easily or hard as you want. With autologging Irssi logs everything to specified directory, one file per channel/nick. ircII style /WINDOW LOG ON is also supported. There's also the "hard way" of logging - /LOG command which lets you specify exactly what you wish to log and where. Log rotating is supported with all the different logging methods, you can specify how often you want it to rotate and what kind of time stamp to use.
· You can most probably ignore anything any way you want. Nick masks, words, regular expressions. You can add exceptions to ignores. You can ignore other people's replies in channels to nicks you have ignored. You can also specify that the specific ignores work only in specific channel(s).
Lastlog and scrollback handling:
· /LASTLOG command has some new features: -new option checks only lines that came since you last did /LASTLOG command, -away option checks new lines since you last went away. Regular expression matches work also, of course. Going to some wanted place at scrollback has always been hard with non-GUI clients. A search command that jumps around in scrollback in GUI-style is still missing from Irssi, but there's something that's almost as good as it. /LASTLOG always shows timestamps when the line was printed, even if you didn't have timestamps on. Now doing /SB GOTO < timestamp > jumps directly to the position in scrollback you wanted. Great feature when you want to browse a bit of the discussion what happened when someone said your name (as seen in awaylog) or topic was changed (/last -topics)
What's New in This Release: [ read full changelog ]
· Add active_window_ignore_refnum option With active_window_ignore_refnum ON, the current behavior for the active_window key (meta-a by default) is preserved: it switches to the window with the highest activity level that was last activated. With active_window_ignore_refnum OFF, the old behavior is used: it switches to the window with the highest activity level with the lowest refnum. (by Matt Sparks, bug #667)
· Show new Charybdis +q list in channel windows (numerics 728 and 729).
· Allow servers to belong to multiple networks.
· Improve paste detection. Irssi now detects a paste if it reads at least three bytes in a single read; subsequent reads are associated to the same paste if they happen before 'paste_detect_time' time since the last read. If no read occurs after 'paste_detect_time' time the paste buffer is flushed; if there is at least one complete line its content is sent as a paste, otherwise it is processed normally.
· Show "target changing too fast" messages in the channel/query window.
· Use default trusted CAs if nothing is specified. This allows useful use of -ssl_verify without -ssl_cafile/-ssl_capath, using OpenSSL's default trusted CAs.
· Show why an SSL certificate failed validation.
· Make own nick and actions use default colour instead of white (by Tim Retout).
· Change some characters illegal in Windows filenames to underscores in logs
· Fix disconnects when sending large amounts of data over SSL
· Show all nicks instead of just the first in an /accept * listing (Bug #704)
· Make several signals without parameters available to perl again. In particular, this includes the "beep" signal (by Matt Sparks, bug #674)
· Close the config file fd after saving (by Sven Wegener)
· Check if an SSL certificate matches the hostname of the server we are connecting to.
· Fix bash'isms, use command -v instead of which and use bc -l in /CALC.
· Fix a crash with handling the DCC queue.
· Fix crash when checking for fuzzy nick match when not on the channel. Reported by Aurelien Delaitre (SATE 2009).