Info Catalog sed: uniq sed: Examples sed: uniq -u

sed: uniq -d

 
 7.18 Print Duplicated Lines of Input
 ====================================
 
 This script prints only duplicated lines, like 'uniq -d'.
 
      #!/usr/bin/sed -nf
 
      $b
      N
      /^\(.*\)\n\1$/ {
          # Print the first of the duplicated lines
          s/.*\n//
          p
 
          # Loop until we get a different line
          :b
          $b
          N
          /^\(.*\)\n\1$/ {
              s/.*\n//
              bb
          }
      }
 
      # The last line cannot be followed by duplicates
      $b
 
      # Found a different one.  Leave it alone in the pattern space
      # and go back to the top, hunting its duplicates
      D
 

Info Catalog sed: uniq sed: Examples sed: uniq -u