How to grab one number from a row in a text but not another number

Mike_V · 04-23-2009, 10:27 PM

Hi there,

I have a text file that contains the following string of numbers and letters:

Code:

Mean track length: 3.45 +/- 1.23 mm

or

Code:

Mean track length: 22.45 +/- 12.23 mm

In the first example, I would like to grab only 3.45 and write it into a new file. Then I would like to grab only 1.23 and write it into another file.
I have 80,000 files to do and those numbers can be different every time.

Thanks for any help/suggestions,

Mike

PS: I'm comfortable with simple grep, sed, awk, and tr scripts but not a hard line programmer.

paulsm4 · 04-23-2009, 10:43 PM

Here's one quick'n'dirty solution:

Quote:

awk '{print $4}' INFILE > OUTFILE

Mike_V · 04-23-2009, 10:58 PM

Hi Paulsm4,
That is just the simplest thing... yep, I like Linux.
And I tried to find a solution to this "problem" in google, without luck, but now: I'm a happy camper.
Thanks a lot!
Mike

ghostdog74 · 04-23-2009, 11:00 PM

Code:

 awk '{print $4 > "newfile1.txt"; print $(NF-1)> "newfile2.txt"}' file

Mike_V · 04-23-2009, 11:07 PM

ghostdog74:

that's an elegant solution...

I have a quick question:

what's a good source to learn about the different codes such as:
$4
NF
(etc?)

Of course from the help I got above, I now know what $4 and NF stand for, but where could I find more?

Thanks,
Mike

Libu · 04-23-2009, 11:22 PM

Google gave me these links:

http://stud.wsi.edu.pl/~robert/awk/.
Theres a section on awk variables.

http://www.vectorsite.net/tsawk.html

ghostdog74 · 04-23-2009, 11:57 PM

Go to the user guide

vikas027 · 04-24-2009, 07:00 AM

hey,

I can help you in another way. But this may help you out in future.

Take your example, you have this line

Code:

Mean track length: 3.45 +/- 1.23 mm

Now, I suppose you have a big file containing these kind of lines.

Code:

for i in `cat file.txt`;

do

(echo $i | awk -F ":" '{print $2}' | awk '{print $1}') > file1
(echo $i | awk -F "-" '{print $2}' | awk '{print $1}') > file2

done;

This is a long code, but it helps you to understand awk a little more ;-)

Also, you can find more awk examples here.

http://www.tldp.org/LDP/abs/html/awk.html
http://www.pathogenomics.sfu.ca/brin...xcmds.html#awk

ghostdog74 · 04-24-2009, 08:00 AM

Quote:

Originally Posted by vikas027

Code:

for i in `cat file.txt`;

do

(echo $i | awk -F ":" '{print $2}' | awk '{print $1}') > file1
(echo $i | awk -F "-" '{print $2}' | awk '{print $1}') > file2

done;

although its another way of doing things, but here are some points to take note nevertheless.
1) using for loop and cat has the potential to break if lines contains spaces (although can be worked around) and you want to capture whole line to variable. Use a while read loop is "better" in this sense.

Code:

while read line
do
....
done < file

2) its great that unix has pipes, but using it like that is inefficient, especially if its a very large file. for every line in file.txt, you have to execute awk twice. tools like awk( grep/sed) already is optimized to loop over files, therefore even without bash's for or while loop, calling awk one time is good enough to process the file.

vikas027 · 04-25-2009, 05:57 AM

Quote:

Originally Posted by ghostdog74

although its another way of doing things, but here are some points to take note nevertheless.
1) using for loop and cat has the potential to break if lines contains spaces (although can be worked around) and you want to capture whole line to variable. Use a while read loop is "better" in this sense.

Code:

while read line
do
....
done < file

2) its great that unix has pipes, but using it like that is inefficient, especially if its a very large file. for every line in file.txt, you have to execute awk twice. tools like awk( grep/sed) already is optimized to loop over files, therefore even without bash's for or while loop, calling awk one time is good enough to process the file.

Thanks for the feedback Ghostdog, frankly I am not very good in shell scripting. My codes are not generally very optimized, but yes I do manage to get things going

But, now I am focusing on make optimized scripts. Its my learning phase