Sort Command in Linux – sort lines of text files

The sort command in Linux sorts lines of input files based on sorting criteria. This command is quite useful for many sysadmins who handle text files daily. In addition to this, the sort command is very flexible and sorts efficiently according to your needs.

One of the advantages of sort is that since it is part of the GNU Core Utils you can use it natively in the system. That is to say, that you do not have to install or to configure something extra.

Like many other commands, the sort command has options that modify its behavior. In this post, we will help you to use them according to the circumstances with examples.

Let’s go for it.

sort syntax

The basic syntax of the sort command is as follows

 sort [option] [file]

or

sort [OPTION]... --files0-from=F

Below are some of common options supported by this command, you can refer man sort page for more details.

• b – ignore leading blanks
• d – dictionary-order (consider only blanks and alphanumeric characters)
• f – ignore case while sorting
• g -general-numeric-sort (compare according to general numerical value)
• i – ignore-nonprinting consider only printable characters
• M – month-sort compare (unknown) < ‘JAN’ < … < ‘DEC’
• h – human-numeric-sort compare human readable numbers (e.g., 2K 1G)
• n – numeric-sort compare according to string numerical value
• R – random-sort shuffle, but group identical keys. –random-source=FILE get random bytes from FILE
• r – reverse reverse the result of comparisons

Using sort command

The basic use of sort command is to sort the file. Let’s consider a file example.txt whose contents are as follows

Motor
Scar
Car
Op

Now, simply run sort command with file name as input.

sort example.txt

You gets an output screen like the following one

Car
Motor
Op
Scar

To reverse the order, use the -r option

sort -r example.txt

This are basic uses. The Sort command support differnet options which change the behavour of the command. Let’s try to cover some common option with examples below.

Sort Command Examples

As I always say, upper and lower case can be a problem in text files. To make the sort ignore them, just use the -f option.

sort -f example.txt

Another useful option is the -u option, which allows us to check if the file is already sorted.

sort -u example.txt

If you do not get any output on the screen, it is already sorted.

If you want to sort and at the same time remove duplicates, you can use the -u option.

sort -u example.txt

Using the -k option and a number, you can specify which field is to be referenced.

For example, let’s start from a file named example2.txt that has the following content

1010 Aaron Trunk
1598 Zac Eron
3578 Fabian mo

We can set it to be sorted by name. That is to say, by the second field of the text line.

sort -k 2 example2.txt

Output:

1010 Aaron Trunk
3578 Fabian mo
1598 Zac Eron

As you can see, it is basic to use the sort command. If you are going to sort numbers, then use the -n option.

sort -n file.txt

You can combine it with the -r option.

sort -nr file.txt

Or if you have a file with months, the right option is -M.

sort -M file.txt

So enjoy it.

More useful commands

Conclusion

In this post, you have learned how to use the sort command to sort text files. Quite useful in configurations and especially for manipulating this kind of files via the terminal.