CODEWITHSUNDEEP
bashparsingshell
tosheikh
tosheikh

Reputation: 65

Reading data from a text file, parsing it and storing it in an array in shell script

I have a text file with matrices

A: 1, 2, 3, 4

B: 2, 4, 6, 8; 1, 2, 5, 6

C: 8, 6, 4, 2; 1, 2, 3, 4; 1, 3, 5, 7

and I want to read this file in shell script, store these matrices in different arrays and then use these arrays for further computation (addition and subtraction only). Here is my code:

#! /bin/bash
R=`awk -F'[^0-9]+' '{$1=$1; print;}' testfile.txt`
echo $R;

this gives me an output in this form:

1 2 3 4 2 4 6 8 1 2 5 6 8 6 4 2 1 2 3 4 1 3 5 7

I tried using loops to put these in different arrays but that didn't work for some reason. Can anyone help me with this?

(i am new to shell scripting so a little explanation with your code solution would be really helpful. thanks)

Upvotes: 1

Views: 1735

Answers (2)

Armali
Armali

Reputation: 19375

This will store the matrix values in the arrays A, B and C:

IFS+=,\;
eval `
while read name numbers
do  if [ $name ]
    then    echo "${name%:}=($numbers)"
    fi
done <testfile.txt
`

This will output the different arrays, just for checking purposes:

echo ${A[*]}
echo ${B[*]}
echo ${C[*]}

Since bash provides only one-dimensional arrays, we have to compute an index given the row size, e. g.

row=2; col=3
echo ${C[$row*4+$col]}

Upvotes: 0

Adam Liss
Adam Liss

Reputation: 48280

One of the Laws of Programming is that parsing input is often more difficult than the entire remainder of the exercise.

To get started, you can try using either cut or the Internal Field Separator several times on each line.

First use : as the delimiter to separate the array name from the values.
Then use ; as the delimiter to separate the rows.
Finally, use , as the delimiter to get the individual values.

Upvotes: 1

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