Remove the blank lines in a text file

Question

In a text file, there are several blank lines and how to remove all of them in a simple way ?

  str="adf{adfadfsa

       dddd sdf sdf,
       dfdsf


       dfsfda


       |df"

After done,

  res="adf{adfadfsa
       dddd sdf sdf,
       dfdsf
       dfsfda
       |df"

Answer 1

The replacement rule "\n" .. -> "\n" will do it, where "\n".. means one or more new lines.

str = "adf{adfadfsa

         dddd sdf sdf,
         dfdsf


         dfsfda


         |df";

StringReplace[str, "\n" .. -> "\n"]

"adf{adfadfsa dddd sdf sdf, dfdsf dfsfda |df"

The same with regular expressions:

StringReplace[str, RegularExpression["\n+"] -> "\n"]

Yet another way:

StringRiffle[StringSplit[str, "\n" ..], "\n"]

And also:

ExportString[DeleteCases[ImportString[str, "Lines"], ""], "Lines"]