sed and grep

ravisingh · #1 02-20-2013

I am stranded with a problem. Please solve.

How will you remove blank lines from a file using sed and grep? ( blank line contains nothing or only white spaces).

I run the below commands of sed and grep but grep isn't giving output as desired. Why?

Code:

sed '/^[ \o11]*$/d' blank

grep -v "^[ \o11]*$" blank

bakunin · #2 02-20-2013

Quote:

Originally Posted by ravisingh

I run the below commands of sed and grep but grep isn't giving output as desired. Why?

Code:

sed '/^[ \o11]*$/d' blank

grep -v "^[ \o11]*$" blank

I suppose it is because of the way you quote. You should probably single-quote the grep-expression as well as you did with the sed-expression.

Quote:

Originally Posted by ravisingh

Also, I am fix at one more place. As, tab is 011 (octal) but in my system the zero of 011 is accepting as o (alphabetic) instead of numeral zero.

You don't need either representation of tabs, as you can enter them directly when you use single-quotes to protect these characters (replace "<spc>" and "<tab>" with literal spaces/tabs when enering the following):

Code:

sed '/^[<spc><tab>]*$/d' blank

versd · #3 04-11-2013

blank lines and whitespaces lines could be removed using this regex:

sed '/^ *$/d'

Don Cragun · #4 04-11-2013

Quote:

Originally Posted by ravisingh

I am stranded with a problem. Please solve.

How will you remove blank lines from a file using sed and grep? ( blank line contains nothing or only white spaces).

I run the below commands of sed and grep but grep isn't giving output as desired. Why?

Code:

sed '/^[ \o11]*$/d' blank

grep -v "^[ \o11]*$" blank

(there is a space before tab in character class)

The above sed command gave desired result but not grep. Why?

Also, I am fix at one more place. As, tab is 011 (octal) but in my system the zero of 011 is accepting as o (alphabetic) instead of numeral zero. If I give numeral zero, it won't work. Is it O.K.? A few days back by mistake a system file got deleted becz of which link count is not showing properly. Can this be a reason for the above problem.

Waiting eagerly for your valuable replies.

Moderator's Comments:

edit by bakunin: please use CODE-tags

I find it hard to believe that either of these commands did what you want. The \o11 needs to be \011 (i.e., digit zero; not lowercase letter oh).

To make it clearer to readers, you could also replace your bracket expression with [[:space:]].

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