greater than a certain value

Shell Programming and Scripting
1

I have an output from db which looks like :

row1   row2    row3 
abc      21.1      13
efg       21.1      45
ghi        21.1      75

when I apply following command ( cat my_output.txt | awk {'print $ 4' }

I have following output :

row3 
13
45
75

now I want to figure out if there is value greater than 70 if yes then create empty file flag.txt
any idea ?
Thanks

2 
awk '{$3 > 70}' my_output.txt > flag.txt
3

Create an empty file flag.txt if there is value greater than 70, whatever if the file flag.txt is exist or not.

awk '$3 > 70 {system ("> flag.txt")} ' my_output.txt
4

hi rdcwayz:
can you please explain the bold section in your logic

awk '$3 > 70 {system ("> flag.txt")} ' my_output.txt

Thanks

5

system ("> flag.txt") => Invokes a shell and executes the command which is within quotes. And you do know what "> flag.txt" does, right?