jq add : Sum or Concatenate an Array

jq add combines all elements of an array with the + operator: summing numbers, concatenating strings or arrays, and merging objects.

add is the quick aggregate when a step needs a total, like the sum of artifact sizes from an API listing.

What it does

add applies + across every element of the input array. Numbers are summed, strings and arrays are concatenated, and objects are shallow-merged. add on an empty array returns null.

Common usage

Terminal

# sum a numeric field across an array
jq '[.[].size] | add' files.json
# total via map
jq 'map(.size) | add' files.json
# concatenate strings
echo '["a","b","c"]' | jq 'add'
# merge an array of objects
jq '.configs | add' settings.json

Functions

Input array of	add returns
numbers	Their sum
strings	Their concatenation
arrays	A single flattened-by-one array
objects	A shallow merge (last key wins)
empty []	null

Common errors in CI

"jq: error: Cannot iterate over null (null)" means add got null, not an array; build the array first with [ ... ]. "jq: error: string (\"5\") and number (3) cannot be added" means the field is a string in the JSON; convert with (.size|tonumber) before summing.

Related guides

jq length : Count Elements or String Sizejq length returns array size, object key count, or string length. Reference for counting gh api results in CI… jq group_by : Group Array Elements by a Keyjq group_by(.field) partitions an array into sub-arrays sharing a key value. Reference for bucketing gh api r… jq map() : Transform Every Array Elementjq map(f) applies a filter to each element of an array and returns a new array. Reference for reshaping gh ap… jq sort_by, min_by and max_by : Order and Pickjq sort_by(.field) orders an array and min_by/max_by pick the extreme element. Reference for ordering gh api…