Re: delete columns csv file

On Apr 4, 4:19=A0am, Ed Morton <mor...@[EMAIL PROTECTED]
> wrote:
=2E.. awk -F, -f file.awk file2.csv file2.csv > newfile

> > Could you tell me which section of the documentation explains why the
fi=
le needs
> > to be read twice, please?
>
> It's not a documentation thing, your problem just requires a 2-pass
soluti=
on.
> The first time to identify which columns always have the null value, the
s=
econd
> to output just the columns that have at least one non-null value.

Thanks for your critism of the so-called tutorial; I'd already
discarded it and started to read the gnu guide to gawk.

Returning to my example: sorry to re-start with this issue of reading
the file twice, would you direct me towards the section of the gawk
guide that explains what you call a "2-pass solution". I'd like to
learn the gawk technical phrase for this task and read the background.

Similarly, I've understood the terms NR and FNR but could not find
reference to the equation NR=3D=3DFNR, which section of the gawk guide
should I read to learn that it is possible to conceive this equation?
As a complete novice, where do I learn that after learning the
definition of NR and FNR independently, it is possible to use these
functions with =3D=3D?

The gawk guide introduces the term 'i++' in section 1.3 but '++' is
explained (correctly?) as increment operator in section 5.8? Why is
increment necessary in this example?

So far, apart from my failure to understand NR=3D=3DFNR, I understand as
follows:

if (NR>1) #if there is a line, or record, go to the next step
for (i=3D1;i<=3DNF;i++) #where there is a record of data, each datum is
considered equivalent to a variable i. As long as i is less than or
equal to the total number of fields, or columns, add a value 1 to the
value of i. So, if my file consists of data arranged in three columns,
for the datum at row 1 column 2, the value of that datum i becomes i
+1.