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help in awk arrays!

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# 1  
Old 09-24-2011
Question help in awk arrays!
Hi, buddies

I am new to shell scripting and trying to solve a problem. I read about arrays in awk that they are quite powerful and are associative in nature.

Awk Gurus Please help!

I have a file:
Code:
Id1 pp1 0t4 pp8 xy2
Id43 009y black
Id6 red xy2
Id12 new pp1 black

I have another file :
Code:
Id pp1 black new pp8

The output should be like: (Ids of file1 and their matching elements from file2)
Code:
Id1 pp1 pp8
Id43 black
Id6 
Id12 new

looking forward for your suggestions.
Cheers!
# 2  
Old 09-24-2011
Code:
$ cat f1
Id1 pp1 0t4 pp8 xy2
Id43 009y black
Id6 red xy2
Id12 new pp1 black

Code:
$ cat f2
Id pp1 black new pp8

Code:
$ nawk  'NR==FNR{for(i=0;++i<=NF;){A[$i]=$i};next}{for(k=0;++k<=NF;){for(j  in A){if($k~A[j]) {x=((length(x))?x" ":x) $k;break}}};print x;x=y}' f2  f1
Id1 pp1 pp8
Id43 black
Id6
Id12 new pp1 black

---------- Post updated at 06:28 PM ---------- Previous update was at 06:08 PM ----------

nawk 'NR==FNR{when scanning the first file
for(i=0;++i<=NFSmilie{loop over all field of lines
A[$i]};store those field in an associative array
next}process next line
{for(k=0;++k<=NFSmilie{Loop over all fields of file to analyse
for(j in A){Loop over the previously built associativ array
if($k~j) {if field match a pattern of associativ array
x=((length(x))?x" ":x) $kThe field is retain to be prompted
breakat first match, go stop looping over the array
} 
}end of field checking over the array
}when all fields have been analyzed
print xprint the concatenation of thos who have been retained
x=yclear x to make it ready for scanning next line
}' f2 f1note that the file contaning the pattern is passed as first argument

could be shorten a little by removing what is in red in previous code.
Code:
nawk  'NR==FNR{for(i=0;++i<=NF;){A[$i]};next}{for(k=0;++k<=NF;){for(j in A){if($k~j) {x=((length(x))?x" ":x) $k;break}}};print x;x=y}' f2  f1

Last edited by ctsgnb; 09-24-2011 at 07:39 PM..
This User Gave Thanks to ctsgnb For This Post:
geli21
# 3  
Old 09-24-2011
Thanks a lot! ctsgnb for such an elaborate explaination. Its very informative for me.
But, I was wondering that the last line is printed as it is because it should be
Code:
Id12 new

otherwise.
# 4  
Old 09-24-2011
Why would that be? All 3 elements (new pp1 black) are in file2, no?
This User Gave Thanks to Scrutinizer For This Post:
geli21
# 5  
Old 09-24-2011
O! Ya! sorry, I even miss wrote in my thread and then just compared it with the same.
Thanks! again.

---------- Post updated at 08:43 PM ---------- Previous update was at 08:34 PM ----------

I have one question. How does it know that the code below is now for second file?
Code:
 
{for(k=0;++k<=NF;)

and can we deal with more than two files with awk?
# 6  
Old 09-24-2011
Quote:
Originally Posted by geli21
---------- Post updated at 08:43 PM ---------- Previous update was at 08:34 PM ----------

I have one question. How does it know that the code below is now for second file?
Code:
 
{for(k=0;++k<=NF;)

and can we deal with more than two files with awk?
1) This is because of the instruction "next", next skip any further code and reprocess next line from the beginning of awk commands

2) yes, awk can deal with more than 2 files, consider the following code :

Code:
$ cat f3
line1
line2
line3
line4
line5

Code:
$ nawk '{print NR,FNR,FILENAME,$0}' f3 f1 f2 f3 f2
1 1 f3 line1
2 2 f3 line2
3 3 f3 line3
4 4 f3 line4
5 5 f3 line5
6 1 f1 Id1 pp1 0t4 pp8 xy2
7 2 f1 Id43 009y black
8 3 f1 Id6 red xy2
9 4 f1 Id12 new pp1 black
10 1 f2 Id pp1 black new pp8
11 1 f3 line1
12 2 f3 line2
13 3 f3 line3
14 4 f3 line4
15 5 f3 line5
16 1 f2 Id pp1 black new pp8

Last edited by ctsgnb; 09-24-2011 at 07:59 PM..
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