[CentOS] Text file manipulation in CentOS?

Dear All
>From my previous posts , I learned from you to make use of 'sort' , 'grep' ,
and 'grep -v' to manipulate text files . At now, I have generated a large
text file from my autoexpect script. To be more specific, I need to find how
many distinct records are there in say column#1? How can I filter out the
distinct records with number of occurances less than a pre-determined
threshold?Can you please show my the power of CentOS in manipulating text
files?
Thank you
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