Read all the entries of a matrix using shell script - linux

Question

I have a matrix,
A(i,j), i=1,m and j=1,n
I can read it in C and FORTRAN, but I can't read it in shell script. I know this is a very simple question, but I am very new to shell script. I want to read all entries and do some calculation e.g. I have a matrix:
A= 1 0 1 1
2 1 0 2
1 0 0 3
1 2 3 0
Now I want to compare each 0 with its above, below, left and right values. Finally I want to do some computation (lets say sum) with these four values around each zero. In the above example the result will be- for five zeros
1st zero: 3
2nd zero: 4
3rd zero: 4
4th zero: 6
5th zero: 6
So in FORTRAN, I can do it by reading all the values as
do j=1,n
do i=1,m
if (A(i,j) .eq. 0) then
B(i,j)=A(i-1,j)+A(i+1,j)+A(i,j+1)+A(i,j-1)
enddo
enddo
But I want to do it in shell script. How to do?

Answer 1

Assuming that data are given in "test.dat" (with no "A = "), I tried it anyway...
#!/bin/bash
inpfile="test.dat"
L=100 # some large value
for (( i = 0; i < L; i++ )) {
for (( j = 0; j < L; j++ )) {
A[ L * i + j ]=0
}
}
i=1
while read buf; do
inp=( $buf ); n=${#inp[#]}
if (( L <= n+1 )); then echo "L is too small"; exit -1; fi
for (( j = 1; j <= n; j++ )) {
A[ L * i + j ]=${inp[j-1]}
}
(( i++ ))
done < $inpfile
nzeros=0
for (( i = 1; i <= n; i++ )) {
for (( j = 1; j <= n; j++ )) {
if (( ${A[ L * i + j ]} == 0 )); then
(( nzeros++ ))
B[ nzeros ]=$(( \
${A[ L * (i-1) + j ]} + \
${A[ L * (i+1) + j ]} + \
${A[ L * i + j+1 ]} + \
${A[ L * i + j-1 ]} ))
fi
}
}
for (( k = 1; k <= nzeros; k++ )) {
printf "%dst zero: %d\n" $k ${B[k]}
}
Conclusion: Very painful. Fortran is recommended...(as expected)