Shell Programming and Scripting

So I'm writing a script to generate pairwise scores for how similar two strings are, and while I've been able to get it to work on a single script, I've been unable to iterate it.

So suppose I have a file thus

Code:

1234567890
1234567890
1234567899

first I need to assign two lines, by their respective line number, to different variables
set $a=1 and $b=3, so I'm interested in a comparison of the first and third lines
I want to pass that into an awk or sed or something bit that will then assign a new variable to the string of that line
so $j=1234567890 (corresponding to $a) and $k=1234567899 (corresponding to b).
I think want to iterate over the values of those lines, so I need something similar to set another two variables to the character in the same place
so then for $i=1 $m=1 and $n=1
and then I do some boolean comparisons and generate a score.

As I said, I need a line that'll do what I need, but take a variable input. I've tried awk ' NR==...' and sed -n, and a few other things, but they don't pass the variable along. What would you recommend?

Code:

$ cat test.sh
# usage: test.sh line1 line2
a=$1 b=$2

# Method #1

j=`sed -n "$a {p; q}" file`
k=`sed -n "$b {p; q}" file`
score=`expr $j - $k` # You substitute real logic

# Method #2

awk 'NR == a { j = $0 } NR == b { k = $0 } END { score = j - k; print score }' file
file

I think what viored didn't understand was how to get a and b into awk:

Code:

awk -v a="$a" -v b="$b" '
NR == a {j = $0}
NR == b {k = $0}
END { score = ...}' file

If $a and $b haven't already been set when you get to awk you can easily replace that first line with:

Code:

awk -v a=1 -v b=3 '

Yes, of course the variables have to be passed into awk. That's what I get for writing a script without testing.

Code:

# usage: test.sh line1 line2
a=$1 b=$2

# Method #1

j=`sed -n "$a {p; q}" file`
k=`sed -n "$b {p; q}" file`
score=`expr $j - $k` # You substitute real logic

# Method #2

awk 'NR == a { j = $0 } NR == b { k = $0 } END { score = j - k; print score }' a=$a b=$b file