Shell Programming and Scripting

Hi forum, I am really hoping somebody can please help me here.

I have a dataset in xyz format, with longitude as x, latitude as y and data readings as z.

eg.

Code:

0 90 -8
1 90 23
2 90 -4
etc etc etc

What i am looking to do is format the data so that x and y are untouched, however in z:

if z > 0 then ignore, else if z < 0 then add 20 to the z value

If anyone knows a better way to accomplish this than an awk command then feel free to contribute. I am very new to unix and am still learning the ropes.

I know the problem most people have in these posts is not conveying their question properly, so i hope mine is understood clearly.

Many thanks in advance, Sam.

You don't need if-else for this. The 'ignore' happens by default anyway, you don't need a case for that.

You can put a condition in front of a code block which will cause it to be executed only when it's true, sort of like an if. Also, you can do math on columns directly.

Code:

awk '($3+0) < 0 { $3 += 20 } 1' filename

The ($3+0) is just to turn the third column, $3, from a string into a number so < > = will work on it as expected.

Thank you!