looping through JSON array in shell script

Extracting the members

jq -c '.children.values[]|[.path.components[0],.type,.size]'

• .children.values[] outputs every member of the array .values.
• | pipes the previous result through the next filter, rather like a shell pipe
• [...,...,...] makes all the terms inside appear in a single array
• The -c option produces "compact" format ie. one object per line

Result:

[".gitignore","FILE",224]
["Jenkinsfile","FILE",1396]
["README.md","FILE",237]
...

Formatting the result

If you want to output a neatly-aligned table, that's a task better handled by other tools, such as column or paste.

jq -c '.children.values[]|[.path.components[0],.type,.size]' | column -t -s'[],"'

• -t tells column to guess the number of columns based on the input
• -s... specifies the delimiter character(s)

Result:

.gitignore   FILE       224
Jenkinsfile  FILE       1396
README.md    FILE       237

This relies on the characters [, ], , and " not appearing in your filenames, which is not a safe assumption.

paste can also arrange multiple inputs side-by-side. For this, we can remove the JSON structures altogether, and output raw lines (hat-tip to @muru):

jq -r '.children.values[]|.path.components[0],.type,.size' | paste - - -

paste - - - means 3 columns, all read from the the same source. This time, the only assumption is that the filenames don't contain newlines.

For the use case provided in the Question, @JigglyNaga's answer is probably better than this, but for some more complicated task, you could also loop through the list items using keys:

from file:

for k in $(jq '.children.values | keys | .[]' file); do
    ...
done

or from string:

for k in $(jq '.children.values | keys | .[]' <<< "$MYJSONSTRING"); do
    ...
done

So e.g. you might use:

for k in $(jq '.children.values | keys | .[]' file); do
    value=$(jq -r ".children.values[$k]" file);
    name=$(jq -r '.path.name' <<< "$value");
    type=$(jq -r '.type' <<< "$value");
    size=$(jq -r '.size' <<< "$value");
    printf '%s\t%s\t%s\n' "$name" "$type" "$size";
done | column -t -s$'\t'

if you have no newlines for the values, you can make it with a single jq call inside the loop which makes it much faster:

for k in $(jq '.children.values | keys | .[]' file); do
    IFS=$'\n' read -r -d '' name type size \
        <<< "$(jq -r ".children.values[$k] | .path.name,.type,.size" file)"
    printf '%s\t%s\t%s\n' "$name" "$type" "$size";
done | column -t -s$'\t'

jq can render its output into a variety of formats: see https://stedolan.github.io/jq/manual/#Formatstringsandescaping

For tab-separated output:

$ jq -r '.children.values[] | [.path.name, .type, .size] | @tsv' file.json
.gitignore  FILE    224
Jenkinsfile FILE    1396
README.md   FILE    237
pom.xml FILE    2548
src DIRECTORY