Appending to a configuration file - bash

Question

I am creating a script which updates hosts in an application, the config file for each host looks like that below. The script generates the hosts correctly but I need to append every } with a comma , except the last host.
I have tried numerous things but the closest I have got is putting the hosts content on a single line and running a IFS statement against it. Im also not sure how best to approach this, can anyone advise?
{
"cmd": "ssh user#webserver",
"inTerminal": "new",
"name": "webserver",
"theme": "basic",
"title": "Webserver",
}
example of what I am trying to achieve
{
"cmd": "ssh user#webserver",
"inTerminal": "new",
"name": "webserver",
"theme": "basic",
"title": "Webserver",
},
{
"cmd": "ssh user#db",
"inTerminal": "new",
"name": "db server",
"theme": "basic",
"title": "db",
},
{
"cmd": "ssh user#mail",
"inTerminal": "new",
"name": "mail server",
"theme": "basic",
"title": "mail server",
}

Answer 1

You can do things like:
#!/bin/sh
for f in $(generate-host-list); do
read -d \000 c < "$f"
list="$list${list+,
}$c"
done
echo "$list"
If you are just writing to a file that can be simpler (no need for the read, just cat the file). Similarly, if you don't care about munging whitespace, you could do list="$list${list+,}$(cat "$f"). If you are using bash or some other shells you can do non-portable things like += to clean it up.

Answer 2

You can do it like this:
sed '$q; s/^}$/},/' <in_file >out_file
The above sed command works as follows: First check if you've reached the last
line, and if so quit. Otherwise, it'll check if the only character on the line
is }, and if so replace it with },.