Convert a txt file into JSON - json

Question

I need to convert a simple txt list into a specific json format.
My list looks like this :
server1
server2
server3
server4
I need to have a JSON output that would look like this :
{ "data": [
{ "{SERVER}":"server1" },
{ "{SERVER}":"server2" },
{ "{SERVER}":"server3" },
{ "{SERVER}":"server4" }
]}
I was able to generate this with a bash script but I don't know how to remove the comma for the last line. The list is dynamic and can have a different amount of servers every time the script is run.
Any tip please ?
EDIT : my current code :
echo "{ "data": [" > /tmp/json_output
for srv in `cat /tmp/list`; do
echo "{ \"{SERVER}\":\"$srv\" }," >> /tmp/json_output
done
echo "]}" >> /tmp/json_output
I'm very new at this, sorry if I sound noobish.

Answer 1

This is very easy for Xidel:
xidel -s input.txt -e '{"data":[x:lines($raw) ! {"{SERVER}":.}]}'
{
"data": [
{
"{SERVER}": "server1"
},
{
"{SERVER}": "server2"
},
{
"{SERVER}": "server3"
},
{
"{SERVER}": "server4"
}
]
}
x:lines($raw) is a shorthand for tokenize($raw,'\r\n?|\n'). It creates an array of every new line.
In human terms you can see x:lines($raw) ! {"{SERVER}":.} as "create a JSON object for every new line".
See also this xidelcgi demo.

Answer 2

I would use jq for this.
$ jq -nR 'reduce inputs as $i ([]; .+[$i]) | map ({"{SERVER}": .}) | {data: .}' tmp.txt
{
"data": [
{
"{SERVER}": "server1"
},
{
"{SERVER}": "server2"
},
{
"{SERVER}": "server3"
},
{
"{SERVER}": "server4"
}
]
}
(It seems to me there should be an easier way to produce the array ["server1", "server2", "server3", "server4"] to feed to the map filter, but this is functional.)
Breaking this down piece by piece, we first create an array of your server names.
$ jq -nR 'reduce inputs as $item ([]; .+[$item])' tmp.txt
[
"server1",
"server2",
"server3",
"server4"
]
This array is fed to a map filter that creates an array of objects with the {SERVER} key:
$ jq -nR 'reduce inputs as $item ([]; .+[$item]) | map ({"{SERVER}": .})' tmp.txt
[
{
"{SERVER}": "server1"
},
{
"{SERVER}": "server2"
},
{
"{SERVER}": "server3"
},
{
"{SERVER}": "server4"
}
]
And finally, this is used to create an object that maps the key data to the array of objects, as shown at the top.

Answer 3

As others said a tool like jq should better be used.
Alternatively, you could use an array and determine whether the element you process is the last or not, for example your code could be :
declare -a servers
servers=($(cat /tmp/list))
pos=$(( ${#servers[*]} - 1 ))
last=${servers[$pos]}
echo "{ "data": [" > /tmp/json_output
for srv in "${servers[#]}"; do
if [[ $srv == $last ]]
then
echo "{ \"{SERVER}\":\"$srv\" }" >> /tmp/json_output
else
echo "{ \"{SERVER}\":\"$srv\" }," >> /tmp/json_output
fi
done
echo "]}" >> /tmp/json_output

Answer 4

You can do this using Python 3 :
#!/usr/local/bin/python3
import os
import json
d = []
with open('listofservers.txt', 'r', encoding='utf-8') as f:
for server in f:
d.append({'{Server}' : server.rstrip("\n")})
print(json.dumps({'data': d}, indent=" "))
Which will print :
{
"data": [
{
"{Server}": "server1"
},
{
"{Server}": "server2"
},
{
"{Server}": "server3"
},
{
"{Server}": "server4"
}
]
}