Ghostdog74

lmedland · 08-14-2008, 11:11 AM

Hi,

You posted on a query I had over a data manipulation task. The code you wrote seems well structured and I would like to understand it a little more.

Code:

awk 'BEGIN{OFS=FS=", "
 c["N"]="01"
 c["C"]="02"
 c["L"]="03"
}
NR==1{print}
NR>1{ 
 print $1,$2, c[substr($3,1,1)] substr($3,2) "01"
}
' file

From what I understand so far, the BEGIN OFS skips the first line. I can see that variable (?) "c" is detailing the first two numbers to use. How does this work?

Then NR displays the first line? Then I get stuck on the substr syntax.

If you could explain a little more it would be helpful. I need to amend the script so that in an event that a code's 3 characters (after the first character) are the same as another codes three characters, the 01 at the end will increment by 1.

Example:-

CBUPP = 02BUP01
CBUPI = 02BUP02
CBUPK = 02BUP03

At the moment the script will obviously produce the following:-

02BUP01
02BUP01
02BUP01

Thanks for the help.

colucix · 08-14-2008, 12:47 PM

I think ghostdog74 is the first LQ member you can search in the thread titles, now!

chrism01 · 08-14-2008, 06:34 PM

Bookmark & read this: http://www.grymoire.com/Unix/Awk.html
Come back if it still isn't clear.

ghostdog74 · 08-14-2008, 07:12 PM

Quote:

Originally Posted by lmedland

From what I understand so far, the BEGIN OFS skips the first line. I can see that variable (?) "c" is detailing the first two numbers to use. How does this work?

the BEGIN{} block is a place where you initialize variables. ie, before awk process the files. "c" is called associative arrays. They are equivalent to this piece of code snippet

Code:

if ( var=="N" ) {
 c="01
}else if ( var=="C" ) {
 c="02"
}

Quote:

Then NR displays the first line? Then I get stuck on the substr syntax.

NR means record number. The first line , NR == 1. Second record, NR==2 and so on. As for substr, you can read about it in the manual (or the one chris provided)

lmedland · 08-17-2008, 08:38 AM

Quote:

Originally Posted by ghostdog74

the BEGIN{} block is a place where you initialize variables. ie, before awk process the files. "c" is called associative arrays. They are equivalent to this piece of code snippet

Code:

if ( var=="N" ) {
 c="01
}else if ( var=="C" ) {
 c="02"
}

NR means record number. The first line , NR == 1. Second record, NR==2 and so on. As for substr, you can read about it in the manual (or the one chris provided)

Thanks for the info everyone.