2D Array using AWK - pls help

Shell Programming and Scripting
1

Hi, i want to write a script using AWK to compare the difference between 2 text file using 2 dimensional array. The script should compare each and every symbol display in the 5 by 5 matrix.
The output should display the coordinates (x,y) of where the difference lies, and displays what is the symbol at Text 1 and symbol at Text 2. Pls help. Thanks

Text 1:

05 *
04 * * *
03 ** * * *
02 * * *
01 *
0 0 0 0 0
1 2 3 4 5

Text 2:

05 &
04 * * *
03 ** * * *
02 * * *
01 *
0 0 0 0 0
1 2 3 4 5

Here, we should be expecting the below output:

Coordinates = (03,05)
Symbol at Text 1 = *
Symbol at Text 2 = &

2

Try and adapt the following awk program cmp.awk :

BEGIN {
   yy[1] = yy[2] = 5;
   for (x=1; x<=5; x++)
      for (y=1; y<=5; y++)
         array[1, x, y] = array[2, x, y] = " ";
}
FNR > 5 {
   next;
}
{
   arr = (NR == FNR ? 1 : 2);
   y   = yy[arr];
   $0  = $0 "     ";
   for (x=1; x<=5; x++) 
      array[arr, x, y] = substr($0, x, 1);
   yy[arr] -= 1;
}
END {
   for (x=1; x<=5; x++)
      for (y=1; y<=5; y++)
         if (array[1, x, y] != array[2, x, y]) {
            printf("Coordinates = (%02d,%02d)\n", x, y);
            printf("Symbol at Text 1 =  %s\n", array[1, x, y]);
            printf("Symbol at Text 2 =  %s\n", array[2, x, y]);
         }
}

The execution of the program gives :

$ cat text1
*
* * *
* * * * *
* * *
*
$ cat text2
&
* * *
* * * * *
* * *
*
$ awk -f cmp.awk text1 text2
Symbol at Text 1 =  *
Symbol at Text 2 =  &
$

Jean-Pierre.

3

which value is belong to file - test1 and test2?

4

Hi Jean, it works!! Thanks.... but i hav some question about the codes...
array[1, x, y] = array[2, x, y] = " "; => is this a 3 D array since there are 3 indexes?

arr = (NR == FNR ? 1 : 2);

yy[arr] -= 1

=> what are these sentences trying to do ?

Thanks in advance

5

I reallise that when i add on another difference to Text 2 , the correct coordinate could not be captured any more.

Text 2:

&

    • *
    • ^ * *
    • *
      *

Output:
$ nawk -f expert_awk text1 text2
Coordinates = (01,05)
Symbol at Text 1 = *
Symbol at Text 2 = &
Coordinates = (05,03) => wrong coordinate!!
Symbol at Text 1 = *
Symbol at Text 2 = ^

Can this script be used for any 5 by 5 matrix comparison or is this just limited to this particular orientation of the matrix ?

6

My awk program considers single char values with no separator in the matrix.
I modify it for space separated values in the matrix (not limited to single caracters).

BEGIN {
   yy[1] = yy[2] = 5;
   for (x=1; x<=5; x++)
      for (y=1; y<=5; y++)
         array[1, x, y] = array[2, x, y] = " ";
}
FNR > 5 {
   next;
}
{
   arr = (NR == FNR ? 1 : 2);
   y   = yy[arr];
   $0  = $0 "     ";
   for (x=1; x<=5; x++) 
      array[arr, x, y] =$x;
   yy[arr] -= 1;
}
END {
   for (x=1; x<=5; x++)
      for (y=1; y<=5; y++)
         if (array[1, x, y] != array[2, x, y]) {
            printf("Coordinates = (%02d,%02d)\n", x, y);
            printf("Symbol at Text 1 =  %s\n", array[1, x, y]);
            printf("Symbol at Text 2 =  %s\n", array[2, x, y]);
         }
}

Now, some explanations :

array[1, x, y] = array[2, x, y] = " ";
array is a 3D array.
array{1] is for text1 and array[2] for text2.
This statement also can be written :
array[1, x, y] = " ";
array[2, x, y] = " ";

arr = (NR == FNR ? 1 : 2);
The ( test ? value1 : value2 ) syntax is the equiv to:
if ( test )
return value1
else
return value2

yy[arr] -= 1
a short cut for
yy[arr] = y[arr] - 1

Jean-Pierre.

7

Here's an alternative in Python:

file1 :

05 *
04 * * *
03 ** * * *
02 * * *
01 *
0 0 0 0 0
1 2 3 4 5

file2:

05 &
04 * * *
03 ** * * *
02 # * $
01 *
0 0 0 0 0
1 2 3 4 5

text1 = open("file1.txt").readlines()
text2 = open("file2.txt").readlines()
for y in range(len(text1)): ## y-coordinates
	if text1[y] != text2[y]:
		t1_splitted  = text1[y].split()
		t2_splitted = text2[y].split()		
		for x in range(5): ## x-coordinates
			try:
				if t1_splitted[x] != t2_splitted[x]:					 
					coordinates = y,x #get coordinates
					print "Coordinates" , coordinates
					print "Symbol at text 1 %s" % t1_splitted[x] 
					print "Symbol at text 2 %s\n" % t2_splitted[x]
					print "-" * 50
			except:pass

Output:

/home> python test.py
Coordinates (0, 1)
Symbol at text 1 *
Symbol at text 2 &

--------------------------------------------------
Coordinates (3, 1)
Symbol at text 1 *
Symbol at text 2 #

--------------------------------------------------
Coordinates (3, 3)
Symbol at text 1 *
Symbol at text 2 $

--------------------------------------------------
8

Thanks Jean for your compreshensive explanation...

I am a beginner in awk so i have a have a couple of questions so as to help me understand the logic and flow of this script more.. :stuck_out_tongue: .Thanks

array[1, x, y] = array[2, x, y] = " ";
array is a 3D array.
array{1] is for text1 and array[2] for text2.
This statement also can be written :
array[1, x, y] = " ";
array[2, x, y] = " ";
Why did you equate the 2 arrays to space which is " " ?

array[arr, x, y] =$x
What is the purpose of this statement ?

FNR > 5 {
next;
What is the logic or flow behind this statement ?

$0 = $0 " ";
What is the purpose of this statement ?

9

Thanks alot ,ghost for the extra info on python!! :wink: