the only reason to use sort and uniq in combination instead of "sort -u" that I can think of is to skip specific columns when looking for unique intances. example: 
...
RH_MEa0001bG06_5    710    14    16    Invalid starting position (14)
RH_MEa0001bG06_4    710    125    12    GGGGGACACCTTCTCTCTCT...
RH_MEa0001bG06_6    710    125    12    GGGGGACACCTTCTCTCTCT...
...

[download]
sending a file containing this output to " | sort | uniq -f1" would compare each line and take the first instance that is unique (other than the column you want to skip, column 1 in this case) up to that point and give you : 
...
RH_MEa0001bG06_4    710    125    12    GGGGGACACCTTCTCTCTCT...
RH_MEa0001bG06_5    710    14    16    Invalid starting position (14)
...

[download]

In reply to Re^3: output unique lines only by l3v3l
in thread output unique lines only by sbp

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