jaq

Extract and transform data with expressions, then explore the results as a tree. Refine an expression while comparing the input and results side by side.

Run a query

vy embeds jaq. It supports extraction and transformation with jq-like expressions without starting an external jq process. Full compatibility with jq is not guaranteed.

Use :jaq <expr> to query the documents you are browsing. For example, extract elements from the items array whose status is failed:

:jaq .items[] | select(.status == "failed")

Running a query from the input or focus view opens the output in a new view for further exploration. :j is an alias. Expressions do not pass through a shell, so you do not need to wrap the entire expression in shell quotes.

Navigate the result tree with j / k and expand or collapse nodes with Space. You can also use / search, :goto, :flatten, :focus, :preview, :copy, :print, and :write.

Extraction and transformation examples

Use expressions to select keys, sort values, and count records. These examples assume a document with an items array.

:jaq .items[] | {name, status}
:jaq .items | sort_by(.duration_ms)
:jaq [.items[] | select(.status == "failed")] | length

Multiple output values are treated as separate result documents. For YAML input, results are also displayed as YAML.

Compare input and results

Press s to display input and results side by side. Compare the original data with the extracted or transformed output. Press s again to show only the results.

Switch the active pane with Tab or the mouse, then navigate and expand or collapse nodes in either pane. Search and the document indices and paths used by regular commands refer to the active pane.

Edit an expression

Press : to open the command editor prefilled with the current jaq <expr>. Edit the expression and press Enter to rerun it, updating the results in the current view. Use Shift+Enter to split long expressions across multiple lines. Press Esc to close the editor.

Rerunning uses the input from when that jaq view was first opened. For example, after filtering down to one record, changing the expression to .items[] | {name, status} extracts keys from every element in the original array. Editing a query does not apply it to the previous results.

You can replace the entire command editor contents to run other commands, such as focus or help.

Rerunning uses the same input regardless of which pane is active, and switches to the result pane after updating. Press Esc while browsing to return to the view that opened jaq.

See Combining focus and jaq to transform a subtree or open part of an extracted result.

Partial results and cancellation

This demo runs a query that keeps producing 0, 1, 2, …. Press G to move to the current end, then Ctrl+C to cancel. Results already produced remain available for browsing.

:jaq 0 | recurse(.+1)

Output values appear as they are produced, before the query finishes. While you edit a command or search, the displayed results are held steady; new results are applied after the interaction.

Ctrl+C requests cancellation of the running query. Cancellation is checked between output values, so it cannot immediately force-stop a computation that produces no output.

You can use :help and :config even with empty results. Commands such as :focus and output commands return an error when there is no selection.

See history to reuse queries, and preview, copy, print, or write to extract results.