sed '/*#/d;/^*$/d' to remove blank lines.

[epikvision]

I've been using vim to do some written homework lately. Yesterday, I encountered a good use for sed.

# Remove comments and blank lines.
sed '/*#/d;/^*$/d'

I wanted to test it out on an assignment to remove some blank lines, but I don't think it's working. Let's say my assignment was foo.txt.

sed '/*foo.txt/d;/^*$/d'

It only results in blank lines themselves until I terminate it. How can I make this work?

[Vaphell]

foo.txt is a file you want to process?

sed 'your expression here' foo.txt

[markbl]

You want to remove comments and blank lines?

sed -e'/^#/d' -e'/^$/d' foo.txt

[epikvision]

Can you explain what /^#/d means? I get that ^$ from start to the end of a line.

[markbl]

Can you explain what /^#/d means? I get that ^$ from start to the end of a line.

Delete any line starting with a "#', i.e. a comment line.

[Vaphell]

^ and $ are start-of-line and end-of-line markers, ^$ simply means 'nothing between start and end (empty line)', while ^# means '# right at the beginning of the line'.

[epikvision]

Is there a special use for this command? I assume it removes all bells and whistles and shows only raw code without any formatting to look at.

[matt_symes]

Hi

Personally i use this as it also strips off # comments in the middle of a line and strips spaces off the end of a line.

sed -e 's/#.*$//' -e 's/[ ]*$//' -e '/^$/d'

matthew-S206:/home/matthew/useful_commands_dir % cat tmp
This
#deb http://ppa.launchpad.net/xorg-edgers/ppa/ubuntu raring main
is


#deb http://ppa.launchpad.net/xorg-edgers/ppa/ubuntu raring main
a test #        test
matthew-S206:/home/matthew/useful_commands_dir % sed -e 's/#.*$//' -e 's/[ ]*$//' -e '/^$/d' tmp
This
is
a test
matthew-S206:/home/matthew/useful_commands_dir %

EDIT: You can use a semi colon as a delimiter as well.

Kind regards

[epikvision]

Wow, it makes things seem pretty darn clean! Thanks for all the posts.