For me, the shell history is mainly used as a completion dict when I press the up arrow. This script removes the lines that does not help serve this purpose

prune_zsh_history.jl

# For me, the history is mainly used as a completion dict when I press the up arrow.
# This script removes the lines that does not help serve this purpose

entries = readlines("$(homedir())/.zsh_history")
commands = Set(readlines(`zsh -ic 'print -rl -- ${(k)aliases} ${(k)functions} ${(k)builtins} ${(k)commands}'`))

filter_but_keep_multiline(f, iter) = let skip = false
    filter(iter) do line
        if skip
            skip = endswith(line, '\\')
            return true
        end
    
        if endswith(line, '\\')
            skip = true
            return true
        end

        f(line)
    end
end

set = Set()
entries = filter_but_keep_multiline(entries) do line
    # 1. remove short (no more than 4 chars) lines
    if length(line) < 20
        return false
    end

    # 2. remove non-existing commands
    content = line[16:end]
    if split(content)[1] ∉ commands
        return false
    end

    # 3. remove duplications
    if content in set
        return false
    else
        push!(set, content)
        return true
    end
end

open("$(homedir())/.zsh_history", "w") do fout
    for line in entries
        println(fout, line)
    end
end