10 Linux cat Command Examples for Beginners

If you are a regular Linux command line user, I am sure you must have used the cat command. The tool is mostly used for displaying the contents of a file, although it provides many other small but useful features. This article will discuss the cat command in detail, explaining some of its key features.

All examples mentioned in this tutorial have been tested on Ubuntu 22.04 LTS.

Linux cat command

The tool's man page describes it as follows: 

cat - concatenate files and print on the standard output

Following are 10 points that'll give you a good idea about cat, including how it works and what features it provides:

1. How to view contents of a file using cat

The cat command allows you to view contents of a file on the standard output (stdout). This can be done in the following way:

$ cat [filename]

For example:

$ cat file1.txt

cat command example

2. How to display multiple files using cat

The tool also allows you to display the contents of multiple files in one go. This can be done in the following way:

$ cat [filename] [filename] ...

For example:

$ cat file1.txt  file2.txt

Show content of several files at once using cat command

3. How to display contents of file with line numbers

If you want, you can also display the contents of a file with line numbers printed at the beginning of each line. This can be done using the tool’s -n command line option.

$ cat -n [filename]

For example:

$ cat -n  file1.txt

Show line numbers when using cat command

4. How to create file using cat command

You can also create a new file and fill it with information using a single cat command. Here's how you do it:

$ cat > [name-of-new-file]

When run, the command requires you to enter the information on the terminal. Once you're done, press CTRL+d.

For example:

$ cat > file4.txt

Use cat command to enter text into a file

To cross-verify the existence of the file as well as check what information it contains, I used the following command:

Show text file content

5. How to copy the contents of one file to another file

You can also use cat to copy the contents of one file to another file. This can be done in the following way: 

$ cat [filename-whose-contents-is-to-be-copied] > [destination-filename]

For example:

$ cat file1.txt > file3.txt

Copy text from one file to another with cat

Please note that the output redirection operator (>) we've used in this case flushes the destination file before the content is moved to it. So, it's worth knowing that another redirection operator (>>) exists that appends the contents to the destination file instead of flushing it first.

6. How to make cat highlight line-ends

If you want, you can also make cat highlight the end of lines. The tool does this by displaying $ at the end of each line. This feature can be accessed using the tool’s -E command line option.

$ cat -E [filename]

For example:

$ cat -E file1.txt

Show line endings in cat command output

7. How to make cat suppress repeated empty lines

If you want, you can also make the cat command suppress repeated empty lines in output. This can be done by using the -s command line option.

$ cat -s [filename]

For example:

$ cat -s file6.txt

Suppress duplicate empty lines in cat command

The first command in the above screenshot shows all the empty lines in the file. But due to the -s command line option we used in the second cat command, the repeated empty lines got suppressed.

8. How to make cat display tab characters as ^I 

The cat command also allows you to display tab characters as ^I. This can be done by using the tool’s -T command line option.

$ cat -T [filename]

For example:

$ cat -T file7.txt

Show tab

As you can see in the above screenshot, the first time around TABs were displayed normally, but when the same command is executed with the -T option, TABs got replaced with ^I.

9. How to make cat display non-printing characters

You can also make the cat command display non-printable characters if you want. This can be done using the -v command line option. 

$ cat -v [filename]

For example:

$ cat -v file9.txt

As you can see in the above screenshot, the first command normally displayed the contents of the file containing non-printable characters. But when we used the -v option, those characters were displayed in a special notation the option uses.

Note that LFD (line feeds) and TAB characters are exceptions for this command line option.

10. The -A option

If you need to use the -v, -E, and -T options together, then instead of writing -vET in the command, you can use the -A command line option.

$ cat -A  [filename]

For example:

$ cat -A file10.txt

As you can see in the screenshot above, the first command shows the file (file10.txt) contains two lines. Those lines contain tabs as well as some non-printable characters. So, when the same command was run with the -A command line option, tabs got replaced by ^I, and non-printing characters were displayed in a special notation. And finally, each line ended with a $. So, effectively, -A did what -vET would have done.

Conclusion

We've covered most cat command options here, so practicing them should give you a pretty good idea about the tool. Do try them out, and once done, head over to the command's man page to learn more about them. 

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