Linux

cat command in Unix/Linux with 10+ examples [2023]

Let’s Learn cat command in Unix/Linux with Practical Examples :

The cat command in Unix/Linux is one of the most commonly used Linux commands on a day-to-day basis whether by novices or experienced Linux users. cat is short for concatenating and is mainly used for creating either single or several files at an instance, or viewing the contents of a file. In this article, we dive deeper and explore the cat command in Unix/Linux with example usages.

Cat command in Linux with examples

The most basic syntax for using cat command is as shown below

$ cat [options] file_name

1	$ cat [options] file_name

Let’s now take a closer look at the options that are mostly used with the cat command.

1. To view file content using cat command

To have a peek at a file without any options, simply use the syntax

$ cat filename

1	$ cat filename

For instance, to check the contents of a file /etc/hosts/code> run the command:

$ cat /var/log/syslog

1	$ cat /var/log/syslog

Sample output

2. View Mutiple files in a single command

To view multiple files at a go with cat command, use the syntax:

$ cat file1 file2

1	$ cat file1 file2

For example

$ cat file1.txt file2.txt

1	$ cat file1.txt file2.txt

Sample output

3. Display line numbers using the -n option

To make your display neater, and more presentable, you may want to number the lines of your output. To achieve this, use the -n option as shown below

$ cat -n file_name

1	$ cat -n file_name

For instance

$ cat -n /etc/passwd

1	$ cat -n /etc/passwd

Sample output

4. Create a file using the cat command

To create a file using cat command use the syntax

$ cat &gt; filename

1	$ cat > filename

Next, type the contents of the file and finally hit CTRL +D to save the file

5. Copy contents of one file onto another

With cat command, you can easily copy file contents of one file into another using the standard redirection operator > as shown below.

$ cat file2.txt  &gt; file3.txt

1	$ cat file2.txt > file3.txt

If the file being copied to does not exist, it will be created automatically.

NOTE

Extra caution should be taken while using the standard redirection operator because it overwrites the contents of an existing file.

6. Redirect several files into one file

Similarly, you can redirect content from multiple files into one file using the syntax:

$ cat file1.txt file2.txt  &gt; file3.txt

1	$ cat file1.txt file2.txt > file3.txt

Sample output

7. Appending text to a file

if you want to append text and not overwrite the existing content, use the double greater sign symbol (>>). The content of one file will be added or appended at the end of the next text file.

$ cat file2.txt &gt;&gt; file3.txt

1	$ cat file2.txt >> file3.txt

8. Redirect standard input using redirection operator

you can use the redirection operator less than (<) to read contents from a file. The syntax for this is:

$ cat < file2.txt

Sample output

9. Display the ‘$’ sign at the end of every line

If you wish to display the $ at the end of every line, use the -e option as shown below:

$ cat -e file3.txt

1	$ cat -e file3.txt

Sample output

From the output above, you can see that there a dollar sign ($) at the end of every file.

10. Display all files of a certain type

To display the content of all files of a certain file type, for example, text files use the wildcard symbol as seen in the command below

$ cat *.txt

1	$ cat *.txt

Sample output

As you can see from the output above, the command displays all content from all the text files with a .txt file extension.

Take away

In this article, we demonstrated the usage of cat command alongside some helpful examples and tips. The cat command is usually helpful in creating and viewing text files as well as appending content at the end of a file. We do hope that this tutorial was helpful. Fee free to try out some of the commands.