What actually the meaning of “-n” in sed?

Question

According to http://linux.about.com/od/commands/l/blcmdl1_sed.htm

suppress automatic printing of pattern space

I\'ve tested wi

Answer 1

$ echo "a b c d" | sed "s/a/apple/"
apple b c d

The pattern space is printed implicitly.

$ echo "a b c d" | sed -n "s/a/apple/"

No output.

$ echo "a b c d" | sed -n "s/a/apple/p"
apple b c d

Explicitly print the pattern space.