[SOLVED] subtracting first column with awk

vincix · 05-05-2017, 12:39 PM

I'm currently reading this: https://docstore.mik.ua/orelly/unix/sedawk/ch07_07.htm
I'm running this script:

Code:

# checkbook.awk
BEGIN { FS = "\t" }

#1 Expect the first record to have the starting balance.
NR == 1 { print "Beginning Balance: \t" $1
	balance = $1
	next		# get next record and start over
}

#2 Apply to each check record, subtracting amount from balance.
{	print $1, $2, $3
	print balance -= $3
}

on this file:

Code:

1000
125	Market          125.45
126	Hardware Store   34.95
127	Video Store       7.45
128	Book Store       14.32
129	Gasoline         16.10

The result is not the same as on the site.
It keeps printing the same '1000' instead of being subtracted:

Code:

Beginning Balance: 	1000
125    Market          125.45
1000
126    Hardware Store   34.95
1000
127    Video Store       7.45
1000
128    Book Store       14.32
1000
129    Gasoline         16.10
1000

I don't understand what is going on exactly.

Turbocapitalist · 05-05-2017, 12:55 PM

It's probably your data or your Field Separator (FS). There appears not to be a tab there between the second and third columns. It looks like a bunch of spaces.

Try this to get the last column, using a default FS instead of a tab:

balance -= $NF

Or else try to figure out a pattern for the FS that will work with the separators you actually have in the file.

Edit: you'll probably want to set the Output Field Separator too:

OFS="\t";

hydrurga · 05-05-2017, 01:32 PM

Quote:

Originally Posted by Turbocapitalist

It's probably your data or your Field Separator (FS). There appears not to be a tab there between the second and third columns. It looks like a bunch of spaces.

Try this to get the last column, using a default FS instead of a tab:

balance -= $NF

Or else try to figure out a pattern for the FS that will work with the separators you actually have in the file.

Edit: you'll probably want to set the Output Field Separator too:

OFS="\t";

Good call. OP, if you change print $1, $2, $3 to print out each of these variables on a separate line, with a * on either end of each variable's value for clarity, you will notice what's happening here.

vincix · 05-05-2017, 01:46 PM

Indeed, that was the problem. The third field in the 3rd line, is 'Store', and not the last field. They aren't tabs, but spaces. iterm2 converts tabs to spaces automatically - it asked me once if it should behave so, and I said yes and that was it