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how to extract data every 20 lines.

how to extract data every 20 lines.# Unix - 噫吁兮，危乎高哉

x*i2004-05-09 07:05

1 楼

I have a data file with 20000 lines. Let me named it as A.dat
But I don't need so many lines of data to draw graph.
I just hope I can extract data from A.dat every 200 lines
and generate a new data file named B.dat and use file B.dat
to do my post-processing job.
Is there any shell command which can implement this job easily?
Thanks for help!

i*n2004-05-09 07:05

2 楼

awk 'NR%20==0 {print $0}' A.dat > B.dat

【在 x***i 的大作中提到】

: I have a data file with 20000 lines. Let me named it as A.dat
: But I don't need so many lines of data to draw graph.
: I just hope I can extract data from A.dat every 200 lines
: and generate a new data file named B.dat and use file B.dat
: to do my post-processing job.
: Is there any shell command which can implement this job easily?
: Thanks for help!

x*i2004-05-09 07:05

3 楼

You are the man! :)
I used script as follows:
lineno=1
while read line
do
lineno=`expr $lineno + 1 `
rest=`expr $lineno % 20`
if [ $rest = 0 ]
then
echo $line
fi
done
echo $lineno
But it executed so slow and it can not work under linux!
By the way, can you use 'sed' command to do it? I am not familiar with
awk....

【在 i*******n 的大作中提到】

: awk 'NR%20==0 {print $0}' A.dat > B.dat