Linux上执行Tcl脚本与Tcl环境下执行脚本，还是有些区别的。（Tcpdump命令）

 

因为工作任务，需要写一个Tcpdump 来显示包的一个脚本。

脚本内容如下：

#！/usr/local/ActiveTcl/bin/tclsh

set package [ exec tcpdump -i eth0 -c 2]

puts $package

# end

在Linux环境下执行结果如下：

root@Server:~/wendh/test# ./tt2.tcl
15:35:27.343648 IP 11.1.1.2 > 22.1.1.2: ICMP echo request, id 60437, seq 32, length 64
15:35:27.343657 IP 22.1.1.2 > 11.1.1.2: ICMP echo reply, id 60437, seq 32, length 64
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
/etc/host.conf: line 1: bad command `Server'
2 packets captured
4 packets received by filter
0 packets dropped by kernel
  while executing
"exec tcpdump -i eth0 -c 2"
  invoked from within
"set a [exec tcpdump -i eth0 -c 2]"
  (file "./tt2.tcl" line 3)
root@Server:~/wendh/test#

而在Tcl环境下执行结果如下：

root@Server:~/wendh/test# tclsh
% source tt2.tcl  
15:37:16.344411 IP 11.1.1.2 > 22.1.1.2: ICMP echo request, id 60437, seq 141, length 64
15:37:16.344420 IP 22.1.1.2 > 11.1.1.2: ICMP echo reply, id 60437, seq 141, length 64
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
/etc/host.conf: line 1: bad command `Server'
2 packets captured
4 packets received by filter
0 packets dropped by kernel
% exit
root@Server:~/wendh/test#

想了很长时间。。也不明白为什么会这样。。会抛出异常。

经朋友提示。。将脚本修改了一下。如下：

#! /usr/local/ActiveTcl/bin/tclsh
catch {exec tcpdump -i eth0 -c 2 } package
puts $package

这样在Linux环境下就不会出现异常。。

如果各位有谁知道为什么会这样。。请给我留言！！！谢谢！！