为什么"exec“会在这段代码中给出”异常退出的子节点“？

Question

我在tcl中运行这段代码：

set version [exec grep "INTERNAL VERSION:" mojave.log | sed -n -e "s/INTERNAL VERSION: //g" > xor.diff]

set p [exec diff ../log.warning.diff ../log.warning.gold >> xor.diff ]

对于最后一行，它在做了一些比较之后给出了以下错误：-

> RULE-311 WARNING: Gdsii layer number 85 datatype 0 has already been defined
> TCL-11   WARNING: Command "check quartz drc" is overridden, Quality Of
> TCL-11   WARNING: Command "delete marker quartz" is overridden, Quality Of
> TCL-11   WARNING: Command "import marker quartz" is overridden, Quality Of
> TCL-11   WARNING: Command "mojave! run filter log" is overridden, Quality Of
> TCL-11   WARNING: Command "run quartz gui" is overridden, Quality Of Results
> TCL-11   WARNING: Command "ui! mojave draw rectangle" is overridden, Quality
> TCL-11   WARNING: Command "ui! mojave set_context" is overridden, Quality Of
> TCL-12   WARNING: Overridden command "mojave! run filter log" is used,
child process exited abnormally
     while executing
"exec diff ../log.warning.diff ../log.warning.gold 2> xor.diff "
     invoked from within
"set p [exec diff ../log.warning.diff ../log.warning.gold 2> xor.diff ]"
     (file "test.tcl" line 4)
     invoked from within
"source test.tcl"

并且它没有在"xor.diff“文件中写入任何内容。

Answer 1

如果命令返回非零，或者如果它向stderr发送任何内容，则exec将返回错误。在http://wiki.tcl.tk/exec上有一个关于结合使用catch和exec的非常深入的讨论

Answer 2

如果发现任何差异，diff (和comm)将退出非零值，因此您可以重定向输出以使用它们，如“to this change?”测试。对于Tcl，你需要使用`|| :‘习惯用法来忽略退出状态。

附言：“grep的无用用法”...sed -n -e '/INTERNAL VERSION: /s//gp'