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loop through file to change some data

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# 1  
Old 05-01-2009
loop through file to change some data
Hi, I have a file with the following data
-0.00000 0.00000 0.00000 F F F
0.00000 0.00000 0.80000 F F F
0.50000 0.50000 0.60000 F F F
0.50000 0.50000 0.20000 F F F
-0.00000 0.00000 0.40000 F F F

I would like to change the last 3 lines from F F F to T T T. I tried looping each line but don't know how to tell it to change the last 3 lines. I wrote this (below) and it changed all the F F F to T T T

for i in tet1
do sed 's/F/T/g' tet1 > tet2
done


How do I change the last 3 lines pls. Thanks in advance
# 2  
Old 05-01-2009
You need to know the last three lines ahead of time
Code:
wc -l tet1 | read lines fname
lines=$(( $lines -2 ))
awk -v lines=$lines ' {  if (NR >= lines) {print $1, $2, $3, "T T T"}
                               else {print $0} 
                            }' tet1 > tet2

# 3  
Old 05-01-2009
Hammer & Screwdriver in my bash shell, the following works
Code:
> cat file14
-0.00000 0.00000 0.00000 F F F
0.00000 0.00000 0.80000 F F F
0.50000 0.50000 0.60000 F F F
0.50000 0.50000 0.20000 F F F
-0.00000 0.00000 0.40000 F F F

> cat -n file14 | tail -3 | awk '{print $1,$2,$3,$4,"T T T"}' >file14.t ;cat -n file14 | head -2 >>file14.t ; sort file14.t | awk '{print $2,$3,$4,$5,$6,$7}'
-0.00000 0.00000 0.00000 F F F
0.00000 0.00000 0.80000 F F F
0.50000 0.50000 0.60000 T T T
0.50000 0.50000 0.20000 T T T
-0.00000 0.00000 0.40000 T T T

# 4  
Old 05-01-2009
Code:
wc -l filename| while read line name
do 
line=$(( $line - 2 ))
awk -v line=$line '{if(NR >= line){gsub(/F/,"T",$0);print
}
else{print}}' filename
done

cheers,
Devaraj Takhellambam
# 5  
Old 05-01-2009
Code:
$
$ cat test1.txt
-0.00000 0.00000 0.00000 F F F
0.00000 0.00000 0.80000 F F F
0.50000 0.50000 0.60000 F F F
0.50000 0.50000 0.20000 F F F
-0.00000 0.00000 0.40000 F F F
$
$ perl -e '{
>   open (F,"test1.txt"); @file = <F>; close (F);
>   for ($i=0; $i<$#file+1; $i++) {
>     if ($i>$#file-3) { $file[$i] =~ s/F/T/g; }
>     print $file[$i]
>   }
> }'
-0.00000 0.00000 0.00000 F F F
0.00000 0.00000 0.80000 F F F
0.50000 0.50000 0.60000 T T T
0.50000 0.50000 0.20000 T T T
-0.00000 0.00000 0.40000 T T T
$
$

HTH,
tyler_durden

______________________________________________
"Only after disaster can we be resurrected."
# 6  
Old 05-02-2009
MySQL It worked for me
Try this one
Code:
cat input | awk 'BEGIN{FS="\n";lines=3}{for (i=1;i<=NF;i++) if (NR >= lines) {gsub(/F/,"T",$0); print} else {print $i}}'

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