Passing a shell / bash variable / environment variable to jq is simple using the native functionality of:
--arg name value or --argjson name value.
How to pass variable to jq filters
This is a generic projects.json file:
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| {
"projects": [
{
"name": "project 1",
"owner": "owner 1",
"id": 1,
"version": "2.3.0"
},
{
"name": "project 2",
"owner": "owner 1",
"id": 2,
"version": "1.54.0"
},
{
"name": "project 3",
"owner": "owner 2",
"id": 3,
"version": "4.9.2"
}
]
}
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String variables
Retrieve project information via a name supplied by a user.
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| echo "Enter name: "
read name
cat projects.json |
jq -r --arg n "$name" '.projects[]|select(.name == $n)'
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Output:
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| Enter name:
project 1
{
"name": "project 1",
"owner": "owner 1",
"id": 1,
"version": "2.3.0"
}
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--arg name value: value is automatically interpreted as a string.
Number variables
Retrieve project information via an id supplied by a user.
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| echo "Enter id: "
read id
cat projects.json |
jq -r --arg id "$id" '.projects[]|select(.id == ($id|tonumber))'
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Output:
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| Enter id:
2
{
"name": "project 2",
"owner": "owner 1",
"id": 2,
"version": "1.54.0"
}
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--arg name value: value must be explicitly converted to a number using the native tonumber function.
Optionally, --argjson name value may be used in jq versions 1.5 or higher. --argjson respects the value type. Following the same example as before,
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| echo "Enter id: "
read id
cat projects.json |
jq -r --argjson id "$id" '.projects[]|select(.id == $id)'
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Output:
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| Enter id:
2
{
"name": "project 2",
"owner": "owner 1",
"id": 2,
"version": "1.54.0"
}
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