diff options
Diffstat (limited to 'doc/chan.n')
| -rw-r--r-- | doc/chan.n | 26 |
1 files changed, 20 insertions, 6 deletions
@@ -287,12 +287,14 @@ slow destinations like network sockets. .RS .PP The \fBchan copy\fR command transfers data from \fIinputChan\fR until -end of file or \fIsize\fR bytes have been transferred. If no -\fB\-size\fR argument is given, then the copy goes until end of file. -All the data read from \fIinputChan\fR is copied to \fIoutputChan\fR. -Without the \fB\-command\fR option, \fBchan copy\fR blocks until the -copy is complete and returns the number of bytes written to -\fIoutputChan\fR. +end of file or \fIsize\fR bytes or characters have been transferred; +\fIsize\fR is in bytes if the two channels are using the same encoding, +and is in characters otherwise. If no \fB\-size\fR argument is given, +then the copy goes until end of file. All the data read from +\fIinputChan\fR is copied to \fIoutputChan\fR. Without the +\fB\-command\fR option, \fBchan copy\fR blocks until the copy is +complete and returns the number of bytes or characters (using the same +rules as for the \fB\-size\fR option) written to \fIoutputChan\fR. .PP The \fB\-command\fR argument makes \fBchan copy\fR work in the background. In this case it returns immediately and the @@ -547,6 +549,18 @@ this, spawn with "2>@" or ">@" redirection operators onto the write side of a pipe, and then immediately close it in the parent. This is necessary to get an EOF on the read side once the child has exited or otherwise closed its output. +.RS +.PP +Note that the pipe buffering semantics can vary at the operating system level +substantially; it is not safe to assume that a write performed on the output +side of the pipe will appear instantly to the input side. This is a +fundamental difference and Tcl cannot conceal it. The overall stream semantics +\fIare\fR compatible, so blocking reads and writes will not see most of the +differences, but the details of what exactly gets written when are not. This +is most likely to show up when using pipelines for testing; care should be +taken to ensure that deadlocks do not occur and that potential short reads are +allowed for. +.RE .VE 8.6 .TP \fBchan pop \fIchannelId\fR |