Awk for Turtlestein: Find duplicates elements in a list

find_duplicates.sh

# Find duplicates in a textual list
#
# Just: 
# * paste the list into Sublime
# * paste this line in Shell Turtlestein (plugin) invite
# * replace $1 by $<element_column_index> if there are more than 1 column
# * add flag -F if columns separator is not default (spaces and tabs)
#
# Can be easily adapted for VIM, it's just awk

| awk '{ items[$1] = items[$1] + 1 } END { for (item in items) { if (items[item] > 1) { print item ": " items[item] } } }' >

<<COMMENT
  2001
  102
  12
  2001
  100

  becomes

  2001: 2
COMMENT