### sort

Suppose you create a data file with name file.txt

Command : 
$ cat > file.txt
abhishek
chitransh
satish
rajan
naveen
divyam
harsh

Sorting a file : Now use the sort command
Syntax :

$ sort filename.txt

Command:
$ sort file.txt

Output :
abhishek
chitransh
divyam
harsh
naveen 
rajan
satish

Note: This command does not actually change the input file, i.e. file.txt.

Sort function with mix file i.e. uppercase and lower case : When we have a mix file with both uppercase and lowercase letters then first the lower case letters would be sorted following with the upper case letters .
Example:
Create a file mix.txt

Command :
$ cat > mix.txt
abc
apple
BALL
Abc
bat

Now use the sort command

Command :
$ sort mix.txt
Output :
abc
Abc
apple
bat
BALL

Options with sort function

1. -o Option : Unix also provides us with special facilities like if you want to write the output to a new file, output.txt, redirects the output like this or you can also use the built-in sort option -o, which allows you to specify an output file.
   Using the -o option is functionally the same as redirecting the output to a file.
   Note: Neither one has an advantage over the other.
   Example:The input file is the same as mentioned above.
   Syntax :

   $ sort inputfile.txt > filename.txt
   $ sort -o filename.txt inputfile.txt

    

   Command:
   $ sort file.txt > output.txt 
   $ sort -o output.txt file.txt
   $ cat output.txt
   
   Output :
   abhishek
   chitransh
   divyam
   harsh
   naveen 
   rajan
   satish
   

2. -r Option: Sorting In Reverse Order : You can perform a reverse-order sort using the -r flag. the -r flag is an option of the sort command which sorts the input file in reverse order i.e. descending order by default.
   Example: The input file is the same as mentioned above.
   Syntax :
   
    
    

   
   

   $ sort -r inputfile.txt

    

   Command :
   $ sort -r file.txt
   Output :
   satish
   rajan
   naveen 
   harsh
   divyam
   chitransh
   abhishek
   

3. -n Option : To sort a file numerically used –n option. -n option is also predefined in unix as the above options are. This option is used to sort the file with numeric data present inside.
   Example :
   Let us consider a file with numbers:

   Command :
   $ cat > file1.txt
   50
   39
   15
   89
   200
   

   Syntax :

   $ sort -n filename.txt

   Command :
   $ sort -n file1.txt
   Output :
   15
   39
   50
   89
   200
   

4. -nr option : To sort a file with numeric data in reverse order we can use the combination of two options as stated below.
   Example :The numeric file is the same as above.
   Syntax :

   $ sort -nr filename.txt

    

   Command :
   $ sort -nr file1.txt
   Output :
   200
   89
   50
   39
   15
   

5. -k Option : Unix provides the feature of sorting a table on the basis of any column number by using -k option.
   Use the -k option to sort on a certain column. For example, use “-k 2” to sort on the second column.
   Example :
   Let us create a table with 2 columns

   $ cat > employee.txt
   manager  5000
   clerk    4000
   employee  6000
   peon     4500
   director 9000
   guard     3000
   

   Syntax :

   $ sort -k filename.txt

   Command :
   $ sort -k 2n employee.txt
   guard    3000
   clerk    4000
   peon     4500
   manager  5000
   employee 6000
   director 9000
   

6. -c option : This option is used to check if the file given is already sorted or not & checks if a file is already sorted pass the -c option to sort. This will write to standard output if there are lines that are out of order.The sort tool can be used to understand if this file is sorted and which lines are out of order
   Example :
   Suppose a file exists with a list of cars called cars.txt.

   Audi
   Cadillac
   BMW
   Dodge
   

   Syntax :

   $ sort -c filename.txt

   Command :
   $ sort -c cars.txt
   Output :
   sort: cars.txt:3: disorder: BMW
    Note : If there is no output then the file is considered to be already sorted 
   

7. -u option : To sort and remove duplicates pass the -u option to sort. This will write a sorted list to standard output and remove duplicates.
   This option is helpful as the duplicates being removed gives us an redundant file.
   Example : Suppose a file exists with a list of cars called cars.txt.

   Audi
   BMW
   Cadillac
   BMW
   Dodge
   

   Syntax :

   $ sort -u filename.txt

   Command :
   $ sort -u cars.txt
   $ cat cars.txt
   Output :
   Audi
   BMW
   Cadillac
   Dodge
   

8. -M Option : To sort by month pass the -M option to sort. This will write a sorted list to standard output ordered by month name.
   Example:
   Suppose the following file exists and is saved as months.txt

   $ cat > months.txt

   February
   January
   March
   August
   September

   Syntax :

   $ sort -M filename.txt

   Using The -M option with sort allows us to order this file.

   Command :
   $ sort -M months.txt
   $ cat months.txt
   Output :
   January
   February
   March
   August
   September