Display unique rows of a file
Given a the following file:
A 1
B 2
A 2
C 3
B 2
D 4
C 1
Create another file in which the first character is unique:
A 1
B 2
C 3
D 4
Given a the following file:
A 1
B 2
A 2
C 3
B 2
D 4
C 1
Create another file in which the first character is unique:
A 1
B 2
C 3
D 4