uniq

#uniq [-cdu][-f<field>][-s<character location>][-w<character location>][--help][--version][input file][output file]

-c or --count shows the number of times the line repeats next to each column.
-d or --repeated displays only the rows and columns that appear repeatedly.
-f<field> or --skip-fields=<field> Ignore the specified field.
-s<character position> or --skip-chars=<character position> Ignore the specified character.
-u or --unique only shows the ranks once.
-w<character position> or --check-chars=<character position> Specifies the character to be compared.
--help Displays help.
--version Displays version information.
[Input File] Specify the sorted text file.
[Output File] Specify the output file.