When using SSH to work on your site, you will often use the cat command. It is used to display file content on the screen. It is one of the most commonly used Linux commands to assist in troubleshooting.
Command: cat
Synopsis: cat [OPTION] [FILE]…
Options:
Below are the different options that are available to customize the cat command.
| Option | Long Name | Description |
|---|---|---|
| -A | –show-all | Equivalent to running the v, E, and T options at the same time (-vET). |
| -b | –number-nonblank | number nonblank output lines |
| -e | equivalent to running the v and E options together (-vE). | |
| -E | –show-ends | displays $ at the end of each line. |
| -n | –number | number all output lines |
| -s | –squeeze-blank | Show no more than a single blank line in a row. |
| -t | equivalent to using v and T options together (-vT). | |
| -T | –show-tabs | display TAB characters as ^I |
| -v | –show-nonprinting | use ^ and M- notation, except for LFD and TAB |
Examples
Using the base cat command
This example uses the base cat command on a file named test.txt. It displays as it is configured in the file. Note that there are two blank lines after the first sentence.
$# cat test.txt Lorem ipsum dolor sit amet, consectetur adipiscing elit. In convallis leo nec lectus accumsan, id vehicula dui tincidunt. Proin eget pellentesque lectus. Duis id mauris vel massa imperdiet egestas sit amet eget ante. Nulla at fermentum turpis. Morbi eu dictum felis. Morbi vel ipsum nunc. Nunc ac sapien viverra, dignissim arcu vitae, gravida magna. Phasellus a adipiscing sapien. Cras vel aliquet massa. Mauris quis auctor eros. Ut gravida tellus at nisi facilisis, adipiscing cursus nisi luctus.Removing extra blank lines
Using the squeeze (-s) option you see that there is only a single blank line displayed after the first sentence.
$# cat -s test.txt Lorem ipsum dolor sit amet, consectetur adipiscing elit. In convallis leo nec lectus accumsan, id vehicula dui tincidunt. Proin eget pellentesque lectus. Duis id mauris vel massa imperdiet egestas sit amet eget ante. Nulla at fermentum turpis. Morbi eu dictum felis. Morbi vel ipsum nunc. Nunc ac sapien viverra, dignissim arcu vitae, gravida magna. Phasellus a adipiscing sapien. Cras vel aliquet massa. Mauris quis auctor eros. Ut gravida tellus at nisi facilisis, adipiscing cursus nisi luctus.View line numbers
If you wish to view the line numbers for the file, simply add the -n option.
$# cat -n test.txt 1 Lorem ipsum dolor sit amet, consectetur adipiscing elit. 2 3 4 In convallis leo nec lectus accumsan, id vehicula dui tincidunt. Proin eget pellentesque lectus. Duis id mauris vel massa 5 imperdiet egestas sit amet eget ante. Nulla at fermentum turpis. 6 7 Morbi eu dictum felis. Morbi vel ipsum nunc. Nunc ac sapien viverra, dignissim arcu vitae, gravida magna. Phasellus a 8 adipiscing sapien. Cras vel aliquet massa. Mauris quis auctor eros. Ut gravida tellus at nisi facilisis, adipiscing cursus nisi luctus.Using multiple options
You can always place options together. In this example, we use the -s and the -n options together. This displays the line numbers as well as removing any extraneous blank lines.
$# cat -ns test.txt 1 Lorem ipsum dolor sit amet, consectetur adipiscing elit. 2 3 In convallis leo nec lectus accumsan, id vehicula dui tincidunt. Proin eget pellentesque lectus. Duis id mauris vel massa 4 imperdiet egestas sit amet eget ante. Nulla at fermentum turpis. 5 6 Morbi eu dictum felis. Morbi vel ipsum nunc. Nunc ac sapien viverra, dignissim arcu vitae, gravida magna. Phasellus a 7 adipiscing sapien. Cras vel aliquet massa. Mauris quis auctor eros. Ut gravida tellus at nisi facilisis, adipiscing cursus nisi luctus.
