Trouble with pipes in chat client on linux


 
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Old 10-24-2012
BTW, pipes do not buffer/delay write() data, but FILE* do delay output until you flush or overflow the buffer, unless you turn on unbuffered or line buffered output (setvbuf()). Graceful exit() flushes all pipes on all but the most crude C compilers.

Pipes are part of IPC, along with signals, shared memory, semaphores, message queues, mmap() of files, sockets. You can inherit a fd such as a pipe or socket from a parent. You can open a named pipe and if someone opens the opposite way (r/w), you are connected 1-1. BTW, you can pass fd down a pipe so another process can attach it. I prefer mmap(): no root requirement, all RAM as a buffer, hard copy after a crash and for a restart, no swap used. Some UNIX/LINUX flavors map socket resources into the file tree. UDP Sockets are neat, as they can broadcast and multicast. A really slick messaging app would multicast, so it scaled really well. When studying IPC, make sure your opinions do not come from way back. Systems have become quite different, and culturally, apps less root entangled.
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chatwidget(3tk) 				      Composite widget for chat applications					   chatwidget(3tk)

__________________________________________________________________________________________________________________________________________________

NAME
chatwidget - Provides a multi-paned view suitable for display of chat room or irc channel information SYNOPSIS
package require Tk 8.5 package require chatwidget ?1.0.0? ::chatwidget::chatwidget path ?options? $widget topic command args $widget name nick args $widget message text args $widget hook command args $widget names args $widget entry args $widget chat args _________________________________________________________________ DESCRIPTION
This is a composite widget designed to simplify the construction of chat applications. The widget contains display areas for chat messages, user names and topic and an entry area. It automatically handles colourization of messages per nick and manages nick completion. A system of hooks permit the application author to adjust display features. The main chat display area may be split for use displaying history or for searching. The widget is made up of a number of text widget and panedwindow widgets so that the size of each part of the display may be adjusted by the user. All the text widgets may be accessed via widget passthrough commands if fine adjustment is required. The topic and names sections can also be hidden if desired. COMMANDS
::chatwidget::chatwidget path ?options? Create a new chatwidget using the Tk window id path. Any options provided are currently passed directly to the main chat text wid- get. WIDGET COMMANDS
$widget topic command args The chat widget can display a topic string, for instance the topic or name given to a multi-user chatroom or irc channel. show Enable display of the topic. hide Disable display of the topic set topic Set the topic text to topic. $widget name nick args Control the names and tags associated with names. list ?-full? Returns a list of all the user names from the names view. If -full is given then the list returned is a list of lists where each sublist is made up of the nick followed by any options that have been set on this nick entry. This may be used to exam- ine any application specific options that may be applied to a nick when using the add command. add nick ?options? delete nick $widget message text args Add messages to the display. options are -nick, -time, -type, -mark -tags $widget hook command args Manage hooks. add (message, post names_group, names_nick, chatstate), remove, run $widget names args Passthrough to the name display text widget. See the text widget manual for all available commands. The chatwidget provides two additional commands show and hide which are used to control the display of this element in the widget. $widget entry args Passthrough to the entry text widget. See the text widget manual for all available commands. $widget chat args Passthrough to the chat text widget. See the text widget manual for all available commands. EXAMPLE
chatwidget::chatwidget .chat proc speak {w msg} {$w message $msg -nick user} .chat hook add post [list speak .chat] pack .chat -side top -fill both -expand 1 .chat topic show .chat topic set "Chat widget demo" .chat name add "admin" -group admin .chat name add "user" -group users -color tomato .chat message "Chatwidget ready" -type system .chat message "Hello, user" -nick admin .chat message "Hello, admin" -nick user A more extensive example is available by examining the code for the picoirc program in the tclapps repository which ties the tcllib picoirc package to this chatwidget package to create a simple irc client. SEE ALSO
text(3tk) KEYWORDS
chat, chatwidget, composite widget, irc, mega-widget, widget chatwidget 1.0.0 chatwidget(3tk)