Smells like homework .. buth .. here is one way: 
perl -pe '$.==6 and $_.="horse\n"' inp.file > out.file

[download]
Assumes you want "horse" AFTER line 6.

        "You're only given one little spark of madness. You mustn't lose it."         - Robin Williams

In reply to Re: How to insert a new line? by NetWallah
in thread How to insert a new line? by Mocky123

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