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awk equivalent script

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# 8  
Old 02-12-2008
OK,
I'll try.

Code:
x[$1]++

While the first field is the same, you have:

Code:
x[$1] is 0 
x[$1] is 1
x[$1] is 2

and so on ...

In Awk an uninitialized variable have the numeric value zero,
that's why when seen for the first time x[$1] is 0.

When the value of $1 changes the cycle is reinitialized.

Code:
$0=NR==1?$0:RS $0

This is a shortcut that I'm using as assignment (and could appear a bit confusing).

It means: assign to $0 (the entire record) the value of RS $0
(the default record separator - newline) and the record itself:
in other words: prepend a newline to the record if the record
is not the first record (otherwise you'll get a newline prepended
to the first record, because x[$1] will be 0).

It's the same as:

Code:
if (NR == 1)
  $0 = $0
else
  $0 = ("\n" $0)

As you know, an awk program looks like this:

Code:
pattern [or expression] { action }

So the above code says:

[pattern/expression]

if x[$1]++ is true: is not 0 (for Awk 0 and NULL are false)

|| (logical OR, double pipe)

$0=NR==1?$0:RS $0 is true (and it's already assigned, while tested Smilie)
(in this case the above expression will always be true, guess whySmilie)

[action]

the action part is omitted which means use the default action:
print the current record.

Hope it makes sense ...


# 9  
Old 02-12-2008
In this case it could be even:

Code:
x[$1]++||$0=NR==1?$0:RS$0

No space between RS and $0 Smilie
# 10  
Old 02-12-2008
Thanks Radoulov - I think I'm going to have to read it thru a few times before it sinks in tho Smilie

...I'm sure I'm on the cusp of really knowing awk so it's worth the time.

Thanks again,

p.
# 11  
Old 02-12-2008
Thanks Radoulov - I think I'm going to have to read it thru a few times before it sinks in tho Smilie

...I'm sure I'm on the cusp of really knowing awk so it's worth the time.

Thanks again,

p.
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