CrLf

如果不要求只调用一次 sed 的话，还是很简单的

sed "s/[0-9a-zA-Z.@]/\n/g" email.txt | sed "/[0-9a-zA-Z.]{1,100}@\w\w*\.\w\w*$/!d"
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batman

太复杂了，目测sed无能为力，下面给出vbs解：

Dim objFSO, Rstr, Arr, Wstr
Set objFSO = CreateObject("Scripting.FileSystemObject")
Rstr = objFSO.OpenTextFile("a.txt").ReadAll
Arr = Split(Rstr, vbCrLf)
For Each str In Arr
  If InStr(1, str, "@gmail.com", 1) Then GetMail(str)
Next
objFSO.OpenTextFile("new.txt", 2, True).Write Wstr
Set objFSO = Nothing
CreateObject("Wscript.Shell").Run "cmd /cstart new.txt", True, True

Function GetMail(Str)
  Dim objReg
  Set objReg = New RegExp
  objReg.Global = True
  objReg.IgnoreCase = True
  objReg.Pattern = "[\s]*.*?\(*([^\(]+@gmail.com).*"
  Wstr = Wstr & objReg.Replace(Str, "$1") & vbCrLf
End Function
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Python

w+([-+.]w+)*@w+([-.]w+)*.w+([-.]w+)*
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正则是这样的