Very Computer

by **gopikrishnan.gunaseka..** » Sun, 12 Feb 2006 02:28:19

hi all,
Im using the following script to select alternative lines from a file.
cat -n <filename> | awk '{ if ($1%2 =0) print $0)
its output contains the line number but i dont want it, Anyone help me
in this regard

Thanks & Regards,
Gopi Krishnan

by **Chris F.A. Johnso** » Sun, 12 Feb 2006 02:51:20

> hi all,
> Im using the following script to select alternative lines from a file.
> cat -n <filename> | awk '{ if ($1%2 =0) print $0)
> its output contains the line number but i dont want it, Anyone help me
> in this regard

awk 'NR % 2 == 0 { print }' FILENAME

--
Chris F.A. Johnson, author | <http://cfaj.freeshell.org>
Shell Scripting Recipes: | My code in this post, if any,
A Problem-Solution Approach | is released under the
2005, Apress | GNU General Public Licence

by **Ed Morto** » Sun, 12 Feb 2006 04:04:16

>>hi all,
>> Im using the following script to select alternative lines from a file.
>>cat -n <filename> | awk '{ if ($1%2 =0) print $0)
>> its output contains the line number but i dont want it, Anyone help me
>>in this regard

> awk 'NR % 2 == 0 { print }' FILENAME

No need for the "{ print }" as that's the default action. I'd go with
just this for odd numbers:

awk 'NR%2' file

and this for even:

awk '(NR+1)%2' file

Regards,

Ed.

by **Chris F.A. Johnso** » Sun, 12 Feb 2006 04:27:07

>>>hi all,
>>> Im using the following script to select alternative lines from a file.
>>>cat -n <filename> | awk '{ if ($1%2 =0) print $0)
>>> its output contains the line number but i dont want it, Anyone help me
>>>in this regard

>> awk 'NR % 2 == 0 { print }' FILENAME

> No need for the "{ print }" as that's the default action.

It's not necessary in this limited script, but it's more
understandable, and easier to deal with when modifying the script
later.

--
Chris F.A. Johnson, author | <http://cfaj.freeshell.org>
Shell Scripting Recipes: | My code in this post, if any,
A Problem-Solution Approach | is released under the
2005, Apress | GNU General Public Licence

by **Ed Morto** » Sun, 12 Feb 2006 04:48:10

>>>>hi all,
>>>>Im using the following script to select alternative lines from a file.
>>>>cat -n <filename> | awk '{ if ($1%2 =0) print $0)
>>>>its output contains the line number but i dont want it, Anyone help me
>>>>in this regard

>>>awk 'NR % 2 == 0 { print }' FILENAME

>>No need for the "{ print }" as that's the default action.

> It's not necessary in this limited script, but it's more
> understandable, and easier to deal with when modifying the script
> later.

Then you should make it "{ print $0 }" for those reasons. Personally I
think it's more useful for people to understand and take advantage of
the default behaviors, especially with small, throwaway scripts.

Ed.

by **Chris F.A. Johnso** » Sun, 12 Feb 2006 07:16:58

>>>>awk 'NR % 2 == 0 { print }' FILENAME

>>>No need for the "{ print }" as that's the default action.

>> It's not necessary in this limited script, but it's more
>> understandable, and easier to deal with when modifying the script
>> later.

> Then you should make it "{ print $0 }" for those reasons.

Perhaps, but I do not need to change the print statement when I
modify the script. If I leave it out, I have to change the script
just to get it to do what it was doing, before I can add things.

Quote:> Personally I think it's more useful for people to understand and
> take advantage of the default behaviors, especially with small,
> throwaway scripts.

When you are familiar with them, by all means use them; I don't
think they're appropriate for someone who has to ask about how to
accomplish a task in the first place. When the experts get into a
"Mine's shorter than yours!" battle, that's different.

--
Chris F.A. Johnson, author | <http://cfaj.freeshell.org>
Shell Scripting Recipes: | My code in this post, if any,
A Problem-Solution Approach | is released under the
2005, Apress | GNU General Public Licence

by **Dan Merce** » Sun, 12 Feb 2006 08:11:26

: hi all,
: Im using the following script to select alternative lines from a file.
: cat -n <filename> | awk '{ if ($1%2 =0) print $0)
: its output contains the line number but i dont want it, Anyone help me
: in this regard
:
: Thanks & Regards,
: Gopi Krishnan
:

To output even numbered lines

awk '!(NR%2)' filename # parentheses necessary since ! has precedence over %

To output odd numbered lines

awk 'NR%2' filename # parentheses necessary since ! has precedence over %

Dan Mercer

by **Bill Marcu** » Sun, 12 Feb 2006 03:30:43

> hi all,
> Im using the following script to select alternative lines from a file.
> cat -n <filename> | awk '{ if ($1%2 =0) print $0)
> its output contains the line number but i dont want it, Anyone help me
> in this regard

awk 'NR%2==0' filename

--
I told my kids, "Someday, you'll have kids of your own." One of them said,
"So will you."
-- Rodney Dangerfield

by **Ed Morto** » Mon, 13 Feb 2006 00:14:55

<snip>
>>Personally I think it's more useful for people to understand and
>>take advantage of the default behaviors, especially with small,
>>throwaway scripts.

> When you are familiar with them, by all means use them; I don't
> think they're appropriate for someone who has to ask about how to
> accomplish a task in the first place. When the experts get into a
> "Mine's shorter than yours!" battle, that's different.

This isn't about brevity. I'm glad the experts I know in various areas
showed me how to do things the way they do rather than the way they
think is good enough for me. At least, I hope they did! It's better to
learn the right way first rather than have to break a bad habit later.

Ed.

by **Chris F.A. Johnso** » Mon, 13 Feb 2006 01:49:47

><snip>
>>>Personally I think it's more useful for people to understand and
>>>take advantage of the default behaviors, especially with small,
>>>throwaway scripts.

>> When you are familiar with them, by all means use them; I don't
>> think they're appropriate for someone who has to ask about how to
>> accomplish a task in the first place. When the experts get into a
>> "Mine's shorter than yours!" battle, that's different.

> This isn't about brevity. I'm glad the experts I know in various areas
> showed me how to do things the way they do rather than the way they
> think is good enough for me. At least, I hope they did! It's better to
> learn the right way first rather than have to break a bad habit later.

The right way isn't necesarily the shortest or most idiosyncratic
way.

--
Chris F.A. Johnson, author | <http://cfaj.freeshell.org>
Shell Scripting Recipes: | My code in this post, if any,
A Problem-Solution Approach | is released under the
2005, Apress | GNU General Public Licence