sort & uniq to remove duplicated line

sort file_name
remove duplicated line : sort file_name | uniq
duplicated line only      : sort file_name | uniq -d
unique line only           : sort file_name | uniq -u
count duplicated line    : sort file_name | uniq -c

example

[sbm@NGS life101]$ more test.txt

aaa

bbb

bbb

bbb

ccc

ddd

[sbm@NGS life101]$ sort test.txt | uniq

aaa

bbb

ccc

ddd

[sbm@NGS life101]$ sort test.txt | uniq -d

bbb

[sbm@NGS life101]$ sort test.txt | uniq -u

aaa

ccc

ddd
[sbm@NGS life101]$ sort test.txt | uniq -c
      1 aaa
      3 bbb
      1 ccc
      1 ddd