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'\"
'\" Copyright (c) 1994 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\" Copyright (c) 2008 Pat Thoyts
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" RCS: @(#) $Id: fileevent.n,v 1.5.8.5 2008/06/26 04:07:36 dgp Exp $
'\" RCS: @(#) $Id: fileevent.n,v 1.5.8.6 2008/10/17 20:52:23 dgp Exp $
'\"
.so man.macros
.TH fileevent n 7.5 Tcl "Tcl Built-In Commands"
.BS
'\" Note: do not modify the .SH NAME line immediately below!
.SH NAME
fileevent \- Execute a script when a channel becomes readable or writable
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\fBfileevent\fR command was invoked.
If an error occurs while executing the script then the
command registered with \fBinterp bgerror\fR is used to report the error.
In addition, the file event handler is deleted if it ever returns
an error; this is done in order to prevent infinite loops due to
buggy handlers.
.SH EXAMPLE
.PP
In this setup \fBGetData\fR will be called with the channel as an
argument whenever $chan becomes readable. The \fBread\fR call will
read whatever binary data is currently available without blocking.
Here the channel has the fileevent removed when an end of file
occurs to avoid being continually called (see above). Alternatively
the channel may be closed on this condition.
.PP
.CS
proc GetData {chan} {
set data [read $chan]
puts "[string length $data] $data"
if {[eof $chan]} {
fileevent $chan readable {}
}
}
fconfigure $chan -blocking 0 -encoding binary
fileevent $chan readable [list GetData $chan]
.CE
.PP
The next example demonstrates use of \fBgets\fR to read line-oriented
data.
.PP
.CS
proc GetData {chan} {
if {[gets $chan line] >= 0} {
puts $line
}
if {[eof $chan]} {
close $chan
}
}
fconfigure $chan -blocking 0 -buffering line -translation crlf
fileevent $chan readable [list GetData $chan]
.CE
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