In this article, we combined the class and Unix uniq commands to identify and eliminate duplicate lines from files text.

Now, you may wonder why we have to use type. The reason is because the uniq command works only with sorted files.

For example, if you had a file that contains
a
b
a

uniq not consider "a" to be duplicated. If the file is sorted as "A" s were together:
a
a
b

then uniq consider the "a" to be duplicated.

Thus, the uniq command can be said to follow the philosophy Unix, which states that programs should be small, designed to do just one thing (well), and interface with other programs to do useful things. By taking that the entry is sorted (so that the duplicate lines are adjacent), uniq creators were able to keep the programming simple and robust - Thus minimizing potential faults and / or unexpected behavior.

Now, let's use an example of a file called "fruit.txt. Contains The following 8 lines:
orange
peach
lime
lemon
lemon
lime
apple
orange

First we want to print the file with each fruit are shown only once - in other words, no duplicates.
We use "fruit.txt sort | uniq" would return:
apple
lemon
lime
orange
peach

Secondly, we print only the fruits duplicative. We use "fruit.txt sort | uniq-d", which would:
lemon
lime
orange

Finally, we can print all the fruits listed once with a count of how many times are listed in the file. We use "fruit.txt sort | uniq-c ":
1 apple
2 lemon
2 lime
2 orange
1 peach

Praveen Puri has been a unix programmer for 19 years. He has a blog called Unix Simplicity that is dedicated to unix shell scripting and awk programming.

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