tcl - 如何检查标准输入在 TCL 中是否可读？

Question

使用以下命令，您可以注册一些回调stdin：

fileevent stdin readable thatCallback

这意味着在执行更新命令期间，thatCallback当有可用输入时，它将一次又一次地评估stdin。

如何检查输入是否可用stdin？

Answer 1

您只需在回调中从标准输入读取/获取。基本上，该模式类似于Kevin Kenny 的 fileevent 示例中的这个片段：

proc isReadable { f } {
  # The channel is readable; try to read it.
  set status [catch { gets $f line } result]
  if { $status != 0 } {
    # Error on the channel
    puts "error reading $f: $result"
    set ::DONE 2
  } elseif { $result >= 0 } {
    # Successfully read the channel
    puts "got: $line"
  } elseif { [eof $f] } {
    # End of file on the channel
    puts "end of file"
    set ::DONE 1
  } elseif { [fblocked $f] } {
    # Read blocked.  Just return
  } else {
    # Something else
    puts "can't happen"
    set ::DONE 3
  }
}
# Open a pipe
set fid [open "|ls"]

# Set up to deliver file events on the pipe
fconfigure $fid -blocking false
fileevent $fid readable [list isReadable $fid]

# Launch the event loop and wait for the file events to finish
vwait ::DONE

# Close the pipe
close $fid

Answer 2

如果您查看此问题的答案，您可以了解如何使用 fconfigure 将通道置于非阻塞模式。这本 Tcl 手册有很多更详细的信息，您需要查看 fconfigure 手册页和 vwait 手册页。