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

This puts sed into quiet mode, where sed will suppress all output except for when explicitly stated by a p command:

   -n 
   --quiet 
   --silent
          By default, sed will print out the pattern space at
          the  end  of  each cycle through the script.  These
          options disable this automatic  printing,  and  sed
          will  only  produce  output when explicitly told to
          via the p command.

An example of this would be if you wanted to use sed to simulate the actions of grep:

$echo -e "a\nb\nc" | sed -n '/[ab]/ p'
a
b

without the -n you would get an occurrence of c (and two occurrences of a and b)