Anthony Takes Note

Often a Linux distribution or software package will add extensive and informative comments to a configuration file. One example of this is the Postfix main.cf file

While the comments can be invaluable, sometimes you want just the basic file without any extras.

To turn a heavily-annotated file into a bare file, you will need to remove 2 sets of lines:

• Any line that begins with a comment symbol (That symbol varies between different applications or programming languages, but it's usually the Hash symbol)
• Any line that is only whitespace.

This is straightforward with the sed command:

cat /etc/postfix/main.cf | sed -e '/^#/d' -e '/^$/d'

• -e simply means “this is a sed command” and is a good way of including multiple commands/searches/etc. That means you don't have to try to merge multiple searches into a single command.
• /search/d means “if the search defined in search matches, delete (d) that line from the output.
• The ^# search means “match lines that have a hashtag at the beginning of the line.”
• The ^$ search means “match lines that have nothing between the start of the line and the end of the line.

Questions? hit me up on Mastodon at @anthonyclarka2@bsd.network.