Data Processing
 

Hey Gang,

I got a pretty quick question. I have a file where blank lines are being used as a place marker, so i cannot remove them:

ex:

train





school" "business
truck


plant



wagon

I would like to put a switch in front of only non- blank lines, while leaving blank lines intact:

ex:


-a train





-a school" "business
-a truck


-a plant



-a wagon


I'm looking for the most simple solution, I am not looking to complicate the script too much as efficiency is a prerequisite.


Thanks KARL

additionally
 

additionally, all non- blank lines do contain at least 1 period.

awk '{if(NF!=0)print "-a",$0; else print $0}' infile

For almost any sort of task involving line-oriented data, awk is your best friend. Definitely an important tool to know.

Solution
 

Hey Gang,

This is the solution I ended up going with:
#########################################

file=data.txt #sets variable file to data.txt

numlines=`wc -l $file | awk '{ print $1 }'` #sets $numlines to the number of lines in $file

r=0 #sets $r to 0

#########################################

while [ $r -le $numlines ]; do #runs loop as many times as there are lines in the file

line=`cat $file | head -$r | tail -1` # $line is equal to the data on the particular line we
## are on in the loop

if [[ $line = *.* ]] #if $line contains anything than a period than anything else
then
echo "-a" $line >> goodfile.txt # prints -a plus the data previous on that line
else
echo >> goodfile.txt # if it does not contain anything a period anything else prints a
## blank line to goodfile.txt
fi

r=`expr $r + 1` #adds 1 to $r
done

###########################################

Any questions feel free to mail.

Thanks for all the help,

-Karl

It will work of course... but you could have done it all with awk. I would encourage you to read-up on it and see how the tool could have been applied to the problem.

*hmmms*

I did use awk, where needed: numlines=`wc -l $file | awk '{ print $1 }'`
That was all it was needed for, the rest was processed through a while loop. ;p

Another possibility would have been to use sed -- something like:

ought to work if each line you want prefixed has a period in it.