create an array like structure if doesn't exists in a file and add content to it in shell scrip-CodePudding

I need to check if an array exists in a file and create it if doesn't exists and add content to it as explained below:

a.txt:

fs.m = [
 abc,
]

Suppose I need to add ‘xyz’ to the array like this:

fs.m = [
 xyz,
 abc,
]

If array doesn’t exists then after creating new array and adding ‘xyz’ to it would look like:

fs.m = [
 xyz,
]

bash script I am using to solve it: add_array_text.sh

#!/bin/bash

if grep -A1 -qE '^fs.m *= *\[' a.txt; then
    echo -e "xyz," >> a.txt
else
    echo -e 'fs.m = [' >> a.txt
    echo -e "xyz," >> a.txt
    echo -e "]" >> a.txt
fi

After execuing add_array_text.sh, a.txt:

fs.m = [
 abc,
]
xyz

This script works fine if array doesn't exists but doesn't as new content is aded after the array if array exists already.

With A1 I tried to get the file context after the match but not able to save it and use it.

Thanks for the help in Advance.

CodePudding user response：

If an array exists, you can do following (assuming file is not too large)


    new_element='xyz'
    cat a.txt | while read line; do
        echo $line >> b.txt
        if [[ $line =~ 'fs.m = [' ]]; then
            echo ${new_element}, >> b.txt
        fi
    done
    mv a.txt a_old.txt
    mv b.txt a.txt

CodePudding user response：

Finally I made it working with below script att_array_text.sh:

#!/bin/bash

if ! grep -q '^fs.m[[:space:]]*=[[:space:]]*\[' a.txt; then
    echo 'fs.m = [' >> a.txt
    echo "xyz," >> a.txt
    echo "]" >> a.txt
else
    sed -i 's/\(^fs.m[[:space:]]*=[[:space:]]*\[\)/\1'"\nxyz,"'/' a.txt
fi