How to Open a File in Read-Only Mode on Linux

In Linux, opening a file in read-only mode can be useful to prevent accidental modifications to the file contents. Read-only mode allows you to view the contents of the file, but you cannot make any changes to it. In this guide, we will show you how to open a file in read-only mode using various Linux commands.

Option 1: Using the less command

The less command is a powerful utility for viewing file contents on Linux. To open a file in read-only mode using less, simply use the “-R” option:

less -R filename

This will open the file in read-only mode, and you can view the contents of the file without the ability to modify it. To exit the less command, press the “q” key.

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Option 2: Using the cat command

The cat command is another popular command for viewing file contents on Linux. To open a file in read-only mode using cat, simply use the “-v” and “-E” options:

cat -vE filename

This will display the contents of the file in read-only mode. The “-v” option will display non-printable characters, and the “-E” option will display a “$” character at the end of each line.

Option 3: Using the view command

The view command is a read-only version of the vi editor. To open a file in read-only mode using view, simply use the “-R” option:

view -R filename

This will open the file in read-only mode, and you can view the contents of the file without the ability to modify it. To exit the view command, press the “q” key.

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Option 4: Using the chmod command

You can also use the chmod command to set the file permissions to read-only mode. To set the file permissions to read-only, use the following command:

chmod 444 filename

This will set the file permissions to read-only mode, and you will not be able to modify the contents of the file. To revert the file permissions back to their original state, use the following command:

chmod 644 filename

Commands Mentioned:

  • less – displays file contents in a paginated manner
  • cat – displays file contents
  • view – opens a file in read-only mode using the vi editor
  • chmod – changes file permissions
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Conclusion:

In this guide, we have shown you how to open a file in read-only mode using various Linux commands. Opening a file in read-only mode can be useful to prevent accidental modifications to the file contents. The less, cat, and view commands allow you to view the contents of a file in read-only mode, while the chmod command allows you to set the file permissions to read-only mode.

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