OS and Software > All Things Unix > grep (awk, sed) help

grep (awk, sed) help

This looks like a job for awk. Here is my first crack at it, I bet it can be improved:

awk code:

#!/usr/bin/awk -f                                                             

BEGIN {
    prev = ""
    skip = "YES"
}

{
    if (/mypattern/) {
        skip = "YES"
    } else {
        if ("NO" == skip) {
            print prev
        }

        prev = $0
        skip = "NO"
    }
}

END {
    if ("NO" == skip) {
        print prev
    }
}

reply to Brano
Hi Brano,

As always, Linux/Unix has many filters to solve the same issue. :)

Here's a solution using sed.

Suppose we have the following text file ....

BOO
a
b
BOO
x
y
z
BOO
black
blue
green
BOO
 

#
# Handle the special case when our token is on line 1.
#
/^BOO$/d

#
# This is the generic case for line 2 .. N
#
/^.*$/{
   N
   /.*\nBOO$/d
   P
   D
}
 

Thank you both. I was able to do what I need using multiple line script, but was hoping for simpler potentially one line solution. ... Pablo, your's the one I guess

FYI: My pattern is never on 1st line so the generic sed should just do perfectly, I'll test it later.

Howdy,

You're welcome ... as a gentle reminder, invoke the sed script using the `-n' parameter: sed -n -f the-script-file file-1 ... file-N



Cheers!
-pablo
--
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reply to Brano
»www.theunixschool.com/2012/06/se···-or.html

Check out #23 in the list, exactly what you want, I think.

Ok guys, thank you for all 3 examples.

The awk posted by Black Box and the sed posted by Uraki are doing what I need.
pablo your is not producing desired output (or I'm doing something wrong).

In any case, mission accomplished, thank you all for help.

Did you try invoke sed as I mentioned in my last post? "sed -n -f the-script-file input-file-1 input-file-2 ... etc"

Thx!
-pablo

reply to Brano
For the sake of completeness, I'll mention that the whole script can be put in a file (let's say myfilter) that if made executable can be executed directly. I takes the same parameters as awk, so if invoked myfilter input.txt it will filter the input.txt file and put the filtered output on the standard output. Pipe or redirect as you wish ;).

--
Keep It Safe, Stupid!
Yes, I CanChat. Can You?

Funny you mention that Black Box as offline, I mentioned the same Brano ...

Incidentally, the issue why my sed script wasn't working was resolved. The Regular Expression Brano used didn't cover the input file.

Cheers,
-pablo
--
openSUSE 12.2/KDE 4.x
ISP: TekSavvy Bonded DSL; backhauled via a 6KM wireless link
Assorted goodies: »pablo.blog.blueoakdb.com