Little explanation needed on array

Shell Programming and Scripting
1

I had gone through..google search.....and unix user post.......where I found so many ways of accessing files..... suppose if I am having 4 files, each file is having 3 columns, and I want to use each field of each column, then how can I use it.. how can I create array for each file's each column, and How do I access each field in C we usually use loops to access data,but C is very lenghty, AWK seems to be simple.. please anyone explain array for handling multiple file

2

Please mention the aim of doing what you are asking, with input and output samples.

3 
HI Dona...you can do something like this if you want to use multiple files
awk '{
          {getline <"file1"; a[NR]=$1;b[NR]=$2;c[NR]=$3} # a,b,c array of File1 column1,column2,column3 
          {getline <"file2"; d[NR]=$1;e[NR]=$2;f[NR]=$3}
          {getline <"file3"; g[NR]=$1;h[NR]=$2;i[NR]=$3}
          {getline <"file4;   j[NR]=$1;k[NR]=$2;l[NR]=$3 }
          }
END{for(i=1;i<=some  value;i++) print a,b,c........}' OFS=" \t" # if you want to  print you can use loop and OFS is tab separated here.

in above example I shown printing of array, you can do you some other operation also.
1 Like
4 
awk 'FNR==1{i++} {for(k=1; k<=NF; k++) A[i,FNR,k]=$k} END{print ".."}' file[1-4]

Would create create a pseudo 3-dimensional array A that can be processed in the END section...

For example: A[2,6,3] will contain the 6th row, 3rd column of the 2nd file.

1 Like
5

Scrutinizer will you please explain #4 with an example...I think I can learn something from you. In fact, I got one problem with nested loop with array only..in following post.
kindly Scrutinizer help me in this post I used your multidimension array method..

6

Thank you Scrutinizer and Akshay.. Scrutinizer's method is effiecient I feel..when there is multiple files, multiple fields...

7

Scrutinizer I wanted to know how to copy 3 dimensional array please give me one example

whether

for(i=1;i<=25;i++)
{
for(m=1;m<=NF;m++)
A[i,m]=A[1,i,m]
}

this is a way to copy or any other ? please reply..

8

The easiest way would be for(X in A) B[X]=A[X]

This works because awk, techically, doesn't have three-dimensional arrays. When you do ARR[A,B,C], it jams A, B, and C together into a single string like A SUBSEP B SUBSEP C.

So you can still loop through them all in a single loop. If you want the individual components of X, you can split them apart on SUBSEP ( a special variable which defaults to an odd, nonprinting ASCII character)

9

Thank you, in my case I think I have to use loop because after each calculation I am storing result in new field

for example

for(i=1;i<=10;i++)
# Dummy calculation
x=A[1,i,5]+...........A[1,i,7]
B[1,i,1]=x
 {
for(m=1;m<=NF;m++)
B[1,i,m+1]=A[1,i,m]
}