Create a single-file "unified format" ovpn file from the legacy client.ovpn client.key client.crt ca.crt four-file format.

README.md

unify-ovpn.sh

1. cd to the directory where your 4 files are. (client.ovpn, client.key, client.crt, and ca.crt)

2. Call unify-ovpn.sh with the filename of your ovpn file

    unify-ovpn.sh client.ovpn
   

3. A new file named client_unified.ovpn will be created

unify-ovpn.sh

#!/bin/bash

src=$1
dst="$(basename $src .ovpn)_unified.ovpn"

gawk -f - $src > $dst << 'AWK'

BEGIN {
    RS="\n|\r\n"
}

function readcert(file) {
    while ((getline < file) > 0) {
        contents = contents RT $0
        if ($1 == "-----BEGIN")
            contents = $0
        if ($1 == "-----END")
            break
    }

    close(file)
    return contents
}

$1 ~ /^(ca|key|cert)$/ {
    tag = $1
    print "#" $0

    print "<" tag ">"
    print readcert($2)
    print "</" tag ">"

    next
}

{
    print
}

AWK