UNIX for Dummies Questions & Answers

Yes indeed! Would you mind translating into English? I don't get how it knows what x is, and I don't see where the shift to the next line happens...Thanks a ton!

I'll try. First, here is the awk script in a slightly different form:

Code:

line 1 awk '
line 2 (NR>1) && (d=$2-x)>=100{print d,NR}
line 3 {x=$2}
line 4 ' file

The line numbers in blue are to make it easy to identify what I'm talking about. They cannot appear in the script.

Line 1 says that we are using awk to perform a sequence of commands on every line of input fed into awk. The single-quotes on lines 1 and 4 contain the awk commands to be evaluated.

The file on line 4 says that input lines to be processed are to be read from a file named file.

Line 2 says that for every line read from file, if the current line number in all of the input files we've read so far is greater than 1 (NR>1) and (&&) after setting d (d=) to be the difference between the 2nd field on this line ($2) and the 2nd field on the previous line (x) it finds that d is greater than or equal to 100 (>=100) it executes the command between the braces which prints the value of d and the current line number (print d,NR).

Since there are no conditions on line 3, the command between braces will be performed on every input line. The command (x=$2) sets x to the value of the 2nd field on the current line. (Note that the commands on the 1st line weren't executed because of the condition (NR>1), but x is set as the last thing to be done on every line read by the command on line 3.)

Lines 2 and 3 are reprocessed in order for every input line read from file.

Note also that you specified (y-x)>=100; not |y-x|>=100. If you meant for the absolute value of the difference to be tested instead, you'll need to adjust the conditions on line 2 and decide if you want the actual difference to be printed or the absolute value of the difference to be printed.

Super impressed, Don. Thank you.