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sort has several optimizations for sorting based on datatypes. This command writes sorted concatenation of all files to standard output. However, be wary, complex sort operations on large files of a few GigaBytes can impede the system performance.

When running a production server with limited CPU and/or memory availability, it is recommended to offload these larger files to a workstation for sorting operations during peak business hours.

Switch	Action
-b	Ignore leading blank lines
-d	Dictionary order, consider only blanks and alphanumeric characters
-f	Ignore case, folding lower and upper characters
-g	General numeric sort
-M	Month sort
-h	Human readable numeric sort 1KB, 1MB, 1GB
-R	Random sort
-m	Merge already sorted files

Feel free to copy the tabular text below and follow along with our sort examples. Be sure each column is separated with a tab character.

first name	last name	office
Ted	Daniel	101
Jenny	Colon	608
Dana	Maxwell	602
Marian	Little	903
Bobbie	Chapman	403
Nicolas	Singleton	203
Dale	Barton	901
Aaron	Dennis	305
Santos	Andrews	504
Jacqueline	Neal	102
Billy	Crawford	301
Rosa	Summers	405
Kellie	Curtis	903
Matt	Davis	305
Gina	Carr	902
Francisco	Gilbert	101
Sidney	Mack	901
Heidi	Simmons	204
Cristina	Torres	206
Sonya	Weaver	403
Donald	Evans	403
Gwendolyn	Chambers	108
Antonia	Lucas	901
Blanche	Hayes	603
Carrie	Todd	201
Terence	Anderson	501
Joan	Parsons	102
Rose	Fisher	304
Malcolm	Matthews	702

Using sort in its most basic, default form −

Sometimes, we will want to sort files on another column, other than the first column. A sort can be applied to other columns with the -t and -k switches.

Note − In some examples, we have used cat piped into grep. This was to demonstrate the concepts of piping commands. Outputting cat into grep can increase the system load hundreds of times over with large files while adding complex sorting. This will make veteran Linux administrators cringe.

Now that we have a good idea of how the pipe character works, this poor practice will be avoided in the chapters to follow. The key to keeping the system resources low with commands like sort is learning to use them efficiently.

Now we have our list sorted by office number. The astute reader will notice something out of the ordinary after the -t switch; single quotes separated by what appears to be a few spaces. This was actually a literal Tab character sent to the shell. A literal Tab can be sent to the BASH shell using the key combination of control+Tab+v.

Most shells will interpret the Tab key as a command. For example, auto-completion in BASH. The shell needs an escape sequence to recognize a literal Tab character. This is one reason why Tabs are not the best choice for delimiters with Linux. Generally speaking, it is best to avoid both spaces and tabs, as they can cause issues when scripting a shell.

Let us fix our names.txt file.

Now, it will be much easier to work with the text file. If someone demands it be returned to Tab-delimited for another application (this is common), we can accomplish that task easily as −

sed -i ‘s/:/\t/g’ ./Documents/names.txt

Common end-user applications will work well with Tabs as a delimiter (An Accountant does not want to see a colon separating data columns while working on Spreadsheets.). So learning to transform characters back and forth is a good practice; it comes up often.

Note − Office uses word-processors and spreadsheets with a Graphical User Interface, running on Windows. Hence, it is common for Linux Administrators to get good at completing transformation actions, accommodating end office users (most times, our boss will be an end-user).

Introduced was a command called sed. sed is a stream editor and can be used as a non-interactive text editor for manipulating streams of text and files. We will learn more about sed later. However, keep in mind, for now, using sed, we avoided a need to pipe several filter commands when changing our text file. Thus, making the most efficient use of the tools at hand.

We also introduced a Bash shell operator: &&. && will run the second command only if the first command completes with a successful status of “0”.

[root@centosLocal centos]# ls /noDir &&  echo “You cannot see me”

ls: cannot access /noDir: No such file or directory

[root@centosLocal centos]# ls /noDir ;  echo “You cannot see me”

ls: cannot access /noDir: No such file or directory

You cannot see me

[root@centosLocal centos]# ls /noDir;  echo “You cannot see me”

In the above code, note the difference between && and;? The first will only run the second command when the first has been completed successfully, while; simply chains the commands. More on this when we get to scripting shell commands.