Question

I’m working on a function to perform multiple key=value substitutions with sed:

batch_sub () {
    local file="${@: -1}" # Last argument is file to be changed.
    [[ -w "${file}" ]] || { echo "Invalid file: ${file}" ; return 1 ; }
    for arg in "${@}" ; do
        [[ $arg =~ (.*)=(.*) ]] || continue
        # 'trim_str' will trim leading & trailing spaces.
        local key=$(trim_str "${BASH_REMATCH[1]}")
        local value=${BASH_REMATCH[2]}
        sed -i 's@'"\(${key}"' *=\).*@\1'"${value}"'@' "${file}"
    done
}

this function accepts arguments like:

batch_sub "a = x" "b = y" "c = z" "a.b.d.e=udp://b:8080" "/tmp/file"

and works fine. But what I want is to make it accept arguments like this:

batch_sub "a = x b = y c = z a.b.d.e=udp://b:8080" "/tmp/file"

Furthermore, it would be nice if sed is invoked only once inside this function:

sed -i -e 's/$key=/\1$value/'
       -e 's/$key1=/\1$value1/'
       '/tmp/file'

please advise.

Answer 1

it would be nice if sed is invoked only once inside this function

You can call sed with multiple substitutions at a time.
e.g.

sed -i ‘s/a/b/;s/p/q/’

So from all the arguments, generate a single string, which involves all the substitutions & then call sed once for all.

But what I want is to make it accept arguments like this
batch_sub “a = x b = y c = z a.b.d.e=udp://b:8080” “/tmp/file”

Why?
“a = x b = y c = z a.b.d.e=udp://b:8080” looks to me as ambiguious.
At least try to have some sort of delimiter for pairs, e.g.
“a = x; b = y; c = z; a.b.d.e=udp://b:8080”