Merge jq output into a comma separated string

Do it in jq

jq -r '.host_components[].HostRoles.host_name | join(",")'

---

No, that's wrong. This is what you need:

jq -r '.host_components | map(.HostRoles.host_name) | join(",")'

Demo:

jq -r '.host_components | map(.HostRoles.host_name) | join(",")' <<DATA
{"host_components":[
  {"HostRoles":{"host_name":"one"}},
  {"HostRoles":{"host_name":"two"}},
  {"HostRoles":{"host_name":"three"}}
]}
DATA

outputs

one,two,three

paste is the best tool to do this job:

your_command | paste -sd, -

If you want to use awk, just print with no newline:

    <your command> | awk 'NR > 1 { printf(",") } {printf "%s",$0}'