Write bash variables into JSON template file

Question

I need, using bash script, create json file with some variables within.

For this purposes, I have a bash file, who creates json template file using cat:

cat <<'EOF' > template.json
{
"ip_range" : "$snmp_ip1", 
"types" : [ "snmp" ],
"description" : "$snmp_cred1",
"snmp.version": "v2c",
"snmp.port" : 161,
"snmp.community" : "$snmp_cred1",
"snmp.retries" : 3,
"snmp.timeout" : 2
}
EOF

Unfortunately, cat does not expand variables into values. So, then I need to insert some variables into template using jq and create some new file with expanded variables. I tried to use jq for this with following code:

jq \
--arg snmp_ip1 "$snmp_ip" \
--arg snmp_cred1 "$snmp_cred" \
'.["snmp_ip1"]=$snmp_ip1 | .["snmp_cred"]=$snmp_cred1' \
<$DIR/template.json >$DIR/cred.json

Unfortunatelly, it just inserts new strings with variables, but not expands variables in template:

{
"snmp_cred": "fortinet/fortigate/1.3.6.1.4.1.12356.101.1.37000_fortigate3700d/10.82.112.21@public",
"snmp_ip1": "10.82.112.21",
"ip_range": "$snmp_ip1",
"types": [
"snmp"
],
"description": "$snmp_cred1",
"snmp.version": "v2c",
"snmp.port": 161,
"snmp.community": "snmp_cred1",
"snmp.retries": 3,
"snmp.timeout": 2
}

Can you hint me, how to rewrite script (or, maybe use another approach) to create json files with this output:

{
"ip_range": "10.82.112.21",
"types": [ "snmp" ],
"description": "fortinet/fortigate/1.3.6.1.4.1.12356.101.1.37000_fortigate3700d/10.82.112.21@public",
"snmp.version": "v2c",
"snmp.port": 161,
"snmp.community": "fortinet/fortigate/1.3.6.1.4.1.12356.101.1.37000_fortigate3700d/10.82.112.21@public",
"snmp.retries": 3,
"snmp.timeout": 2
}

Jack Bracken · Accepted Answer · 2016-10-19 11:16:54Z

3

Remove the quotes around your delimieter EOF as this causes cat to not expand variables.

answered Oct 19, 2016 at 11:16

Jack Bracken

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3 Comments

Vasyl Stepulo Over a year ago

When I changed it to: cat <<EOF > template.json - it just delete variables from template. For example - "ip_range" : "",

Jack Bracken Over a year ago

What does echo $snmp_ip1 immediately before the cat return?

Vasyl Stepulo Over a year ago

Oh, my fault. I've just entered wrong variable names in cat section. Thanks, your advice works!

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