diff options
Diffstat (limited to 'doc/close.n')
| -rw-r--r-- | doc/close.n | 25 |
1 files changed, 15 insertions, 10 deletions
diff --git a/doc/close.n b/doc/close.n index 60a8b97..2826d82 100644 --- a/doc/close.n +++ b/doc/close.n @@ -5,8 +5,6 @@ '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" -'\" RCS: @(#) $Id: close.n,v 1.16 2009/04/15 12:31:24 dkf Exp $ -'\" .so man.macros .TH close n 7.5 Tcl "Tcl Built-In Commands" .BS @@ -25,7 +23,8 @@ Tcl standard channel (\fBstdin\fR, \fBstdout\fR, or \fBstderr\fR), the return value from an invocation of \fBopen\fR or \fBsocket\fR, or the result of a channel creation command provided by a Tcl extension. .PP -The single-argument form is a simple "full-close": +The single-argument form is a simple +.QW "full-close" : all buffered output is flushed to the channel's output device, any buffered input is discarded, the underlying file or device is closed, and \fIchannelId\fR becomes unavailable for use. @@ -49,8 +48,10 @@ When the last interpreter in which the channel is registered invokes \fBinterp\fR command for a description of channel sharing. .PP Channels are automatically closed when an interpreter is destroyed and -when the process exits. Channels are switched to blocking mode, to ensure -that all output is correctly flushed before the process exits. +when the process exits. +.VS 8.6 +From 8.6 on (TIP#398), nonblocking channels are no longer switched to blocking mode when exiting; this guarantees a timely exit even when the peer or a communication channel is stalled. To ensure proper flushing of stalled nonblocking channels on exit, one must now either (a) actively switch them back to blocking or (b) use the environment variable TCL_FLUSH_NONBLOCKING_ON_EXIT, which when set and not equal to "0" restores the previous behavior. +.VE 8.6 .PP The command returns an empty string, and may generate an error if an error occurs while flushing output. If a command in a command @@ -58,16 +59,20 @@ pipeline created with \fBopen\fR returns an error, \fBclose\fR generates an error (similar to the \fBexec\fR command.) .PP .VS 8.6 -The two-argument form is a "half-close": given a bidirectional channel like a +The two-argument form is a +.QW "half-close" : +given a bidirectional channel like a socket or command pipeline and a (possibly abbreviated) direction, it closes -only the substream going in that direction. This means a shutdown() on a +only the sub-stream going in that direction. This means a shutdown() on a socket, and a close() of one end of a pipe for a command pipeline. Then, the Tcl-level channel data structure is either kept or freed depending on whether the other direction is still open. .PP -A single-argument close on an already half-closed bi-channel is defined to -just "finish the job. A half-close on an already closed half, or on a -wrong-sided unidirectional channel, raises an error. +A single-argument close on an already half-closed bidirectional channel is +defined to just +.QW "finish the job" . +A half-close on an already closed half, or on a wrong-sided unidirectional +channel, raises an error. .PP In the case of a command pipeline, the child-reaping duty falls upon the shoulders of the last close or half-close, which is thus allowed to report an |