Tcl/Expect中利用exec调用稍微复杂的shell命令时，经常会遇到一些小问题，常见的就是pipeline(|)和awk。
Tcl/Expect调用多个shell命令并使用|将其串接在一起时，需要注意的是必须在"|"前后加上空格" "，否则tcl/Expect会报奇怪的错。
Tcl/Expect调用awk命令时，需要把awk的' '中的命令改为用" "，并把$1, $2之类的变量改为/$1, /$2。
下面的ksh命令判断test_process是否在运行：
ps -fu bonny|grep -v ps|grep MMCAP|grep -v grep|awk '{print $2}'
改为Tcl/Expect后，为：
exec ps -fu $myname | grep -v ps | grep COOLrunMMCAP | grep -v grep | awk "{print /$2}"
另外， http://www.linuxquestions.org/questions/linux-software-2/ksh-tcl-173092/ 列出了一些ksh命令转换为tcl语句时经常遇到的问题（本人未曾验证过，请谨慎使用）。
Here's some conversion rules that I have proven, if anyone has any more info ( in any fashion ) , please advise.
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Rule: Remove "
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ksh: cat *.passwd 2>/dev/null | cut -d":" -f1 | sort | uniq
tcl: exec cat *.passwd 2>/dev/null | cut -d: -f1 | sort | uniq
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Rule: Replace '(..$1..)' with "{../$1..}"
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ksh: ps -eaf | awk '(print $1}' | grep $1 2>&1
tcl: exec ps -eaf | awk "{print /$1}" | grep $user_login_to_test
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Rule: Replace "..." with {...}
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ksh: grep "^$(user_login:" /etc/passwd /etc/shadow 2>&1
tcl: exec grep {^$user_login:} /etc/passwd /etc/shadow
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Rule: Replace '...' with "..." or {...}
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ksh: grep 'Version' user.tcl
tcl: exec grep {Version} user.tcl
tcl: exec grep "Version" user.tcl
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还有就是http://wiki.tcl.tk/1039列出了使用exec的一些常见问题。