How to update matrix-like-data (.txt) file in bash programming?

I am new to bash programming. I have this file, the file contain is:

   A B C D E
 1 X 0 X 0 0
 2 0 X X 0 0
 3 0 0 0 0 0
 4 X X X X X

Where X means, it has value, 0 means its empty.

From there, let say user enter B3, which is a 0, means I will need to 开发者_运维技巧replace it to X. What is the best way to do it? I need to constantly update this file.

FYI: This is a homework question, thus please, dont give a direct code/answer. But any sample code like (how to use this function etc) will be very much appreciated).

Regards,

Newbie Bash Scripter

EDIT:

If I am not wrong, Bash can call/update directly the specific column. Can it be done with row+column?

If you can use sed I'll throw out this tidbit:

sed -i "/^2/s/. /X /4" /path/to/matrix_file

Input

  A B C D E
1 0 0 0 0 0
2 X 0 0 X 0
3 X X 0 0 X

Output

  A B C D E
1 0 0 0 0 0
2 X 0 X X 0
3 X X 0 0 X

Explanation

^2: This restricts sed to only work on lines which begin with 2, i.e. the 2nd row

s: This is the replacement command

Note for the next two, '_' represents a white space

._: This is the pattern to match. The . is a regular expression that matches any character, thus ._ matches "any character followed by a space". Note that this could also be [0X]_ if you are guaranteed that the only two characters you can have are '0' and 'X'

X_: This is the replacement text. In this case we are replacing 'any character followed by a space' as described above with 'X followed by a space'

4: This matches the 4th occurrence of the pattern text above, i.e. the 4th row including the row index.

What would be left for you to do is use variables in the place of ^2 and 4 such as ^$row and $col and then map the letters A - E to 1 - 5

something to get you started

#!/bin/bash
# call it using ./script B 1
# make it executable using "chmod 755 script"

# read input parameters

col=$1
row=$2

# construct below splits on whitespace
while read -a line
do
    for i in ${line[@]}; do
        array=( "${array[@]}" $i );
    done
done < m

# Now you have the matrix in a one-dimensional array that can be indexed.

# Lets print it

for i in ${array[@]}; do
    echo $i;
done

Here's a starter for you using AWK:

awk -v col=B -v row=3 'BEGIN{getline; for (i=1;i<=NF;i++) cols[$i]=i+1} NR==row+1{print $cols[col]}'

The i+1 and row+1 account for the row heading and column heading, respectively.