How to View Configuration Files Without Comments in Linux?

In this article, I'll show you how to view configuration files without comments in Linux using a few simple commands. Removing comments from configuration files can help you more easily find the information you need and make modifications to system settings. We'll explore two methods to accomplish this task - using the grep and sed commands. With these methods, you can effortlessly streamline your Linux system's configuration files, making it easier to locate critical information and adjust settings as needed.

If you need to remove comments from a configuration file in Linux, the grep command is a straightforward and efficient solution. Often used for pattern searching in files, grep can also filter out lines that begin with the comment character. In most Linux systems, the hash symbol (#) is the designated comment character for configuration files.

Method 1: Using Grep Command

To remove comments from a configuration file using grep, you can run the following command in your linux terminal −

grep -v '^#' /path/to/config/file

Here is an example of the terminal output −

Port 22
AddressFamily any
ListenAddress 0.0.0.0
ListenAddress ::

In order to filter out lines starting with the hash symbol (#) from a configuration file and show only the remaining contents, the command utilizes the ^ symbol to match the start of a line. By doing so, the command ensures that only lines starting with the hash symbol at the beginning of the line are excluded.

Let's take an example configuration file and see how this command works. Consider the following configuration file for the Apache web server (/etc/httpd/conf/httpd.conf) −

# This is the main configuration file for the Apache HTTP server
#
# ServerRoot: The top of the directory tree under which the server's
# configuration, error, and log files are kept.
#
ServerRoot "/etc/httpd"

# Listen: Allows you to bind Apache to specific IP addresses and/or
# ports, instead of the default. See also the 
# directive.
#
# Listen 12.34.56.78:80
Listen 80

# LoadModule: Controls which modules are loaded at startup.
LoadModule auth_basic_module modules/mod_auth_basic.so
LoadModule auth_digest_module modules/mod_auth_digest.so
LoadModule authn_file_module modules/mod_authn_file.so

If we run the grep command on this file like so −

grep -v '^#' /etc/httpd/conf/httpd.conf

The output will be −

ServerRoot "/etc/httpd"

Listen 80

LoadModule auth_basic_module modules/mod_auth_basic.so
LoadModule auth_digest_module modules/mod_auth_digest.so
LoadModule authn_file_module modules/mod_authn_file.so
...

As you can see, the output only includes the non-commented lines of the configuration file.

Method 2: Using Sed Command

Another option to remove comments from a configuration file is to use the sed command. sed stands for stream editor and can be used to perform basic text transformations on an input stream.

To remove comments from a configuration file using sed, we can use the following command −

sed '/^#/d' /path/to/config/file

For example, let's assume we have the following configuration file −

# This is the main configuration file for the Apache HTTP server
#
# ServerRoot: The top of the directory tree under which the server's
# configuration, error, and log files are kept.
#
ServerRoot "/etc/httpd"

# Listen: Allows you to bind Apache to specific IP addresses and/or
# ports, instead of the default. See also the <VirtualHost>
# directive.
#
# Listen 12.34.56.78:80
Listen 80

# LoadModule: Controls which modules are loaded at startup.
LoadModule auth_basic_module modules/mod_auth_basic.so
LoadModule auth_digest_module modules/mod_auth_digest.so
LoadModule authn_file_module modules/mod_authn_file.so

If we run the command "sed '/^#/d' sample.conf", we would expect to see the following output in the terminal −

LoadModule auth_basic_module modules/mod_auth_basic.so
LoadModule auth_digest_module modules/mod_auth_digest.so
LoadModule authn_file_module modules/mod_authn_file.so

This is because the "sed" command removes any lines that begin with a "#" symbol, effectively filtering out any comments from the file. The output only includes the lines that contain actual configuration settings without comments.

This command will remove any lines that begin with the hash symbol (#) from the configuration file. The d command is used to delete lines that match the specified pattern.

Using the same example configuration file as before, if we run the sed command like so −

sed '/^#/d' /etc/httpd/conf/httpd.conf

The output will be −

ServerRoot "/etc/httpd"

Listen 80

LoadModule auth_basic_module modules/mod_auth_basic.so
LoadModule auth_digest_module modules/mod_auth_digest.so
LoadModule authn_file_module modules/mod_authn_file.so

As you can see, the output is the same as the grep command output.

Conclusion

In conclusion, as Linux users, we understand how comments in configuration files can sometimes be a hindrance rather than a help when trying to locate the information we need. However, there are simple commands such as grep and sed that can remove comments from configuration files, leaving only the essential information. Additionally, some text editors also have the ability to hide or remove comments in configuration files. By removing comments, it becomes easier to modify system settings and troubleshoot issues, simplifying the overall Linux experience.