Using JMESPath Queries in the Globus CLI

The Globus CLI supports using JMESPath queries to filter and transform the output of commands. JMESPath is a query language for JSON with its own specification and syntax.

To learn more about JMESPath, consider reading the JMESPath Tutorial.

The --jmespath Option

All Globus CLI commands support a --jmespath option which takes a JMESPath query as an argument. The command’s JSON output will be processed with the query before being emitted.

For example, it can be used to extract the task_id from a globus transfer task submission:

$ globus transfer $source $dest --batch $data --jmespath 'task_id'
"37fda17c-d07a-4004-8818-3067862ba8e3"
Tip

We also support --jq, for "json query", as an alias for --jmespath!

Combining --jmespath with --format=UNIX

JMESPath output is still JSON data. That means that strings are quoted, arrays are wrapped in brackets, and commas are used as separators.

The CLI supports an alternative output format, designed to be combined with --jmespath to produce output in a format more easily consumed by standard UNIX tools. Using --format UNIX will emit data with quotes stripped, using tabs and newlines as separators.

For example, taking the example above and adding --format UNIX:

$ globus transfer $source $dest --batch $data --jmespath 'task_id'
37fda17c-d07a-4004-8818-3067862ba8e3

In turn, this lets us use the output in a pipeline, subshell, or other context:

$ task_id="$(globus transfer $source $dest --batch $data --jmespath 'task_id')"
$ globus task wait $task_id --timeout 1800
$ globus task wait "$(globus transfer $source $dest --batch $data --jmespath 'task_id')" --timeout 1800
Tip

The --format option is also available as -F, supports "slamming", and is case insensitive. So you can abbreviate --format=UNIX as -F UNIX or -Funix.

Exploring output with --format JSON

In order to use --jmespath effectively, you need to know what the JSON data for a given command is.

A great way to explore is to start with --format JSON to see the raw JSON and then to process that result with JMESPath queries.

For example, one might start with

$ globus group list --format JSON
...

to see the output, and then use JMESPath on the result. Perhaps to write a script:

#!/bin/bash
echo 'List My Groups:'
globus group list \
    --jmespath '[].[name, id]' \
    -Funix | \
  awk -F'\t' '{print $1, "("$2")"}'