The fab tool is very verbose by default and prints out almost everything it can, including the remote end’s stderr and stdout streams, the command strings being executed, and so forth. While this is necessary in many cases in order to know just what’s going on, any nontrivial Fabric task will quickly become difficult to follow as it runs.
To aid in organizing task output, Fabric output is grouped into a number of non-overlapping levels or groups, each of which may be turned on or off independently. This provides flexible control over what is displayed to the user.
All levels, save for debug, are on by default.
The standard, atomic output levels/groups are as follows:
Changed in version 0.9.2: Added “Executing task” lines to the running output level.
Changed in version 0.9.2: Added the user output level.
There is a final atomic output level, debug, which behaves slightly differently from the rest:
debug: Turn on debugging (which is off by default.) Currently, this is largely used to view the “full” commands being run; take for example this run call:
run('ls "/home/username/Folder Name With Spaces/"')
Normally, the running line will show exactly what is passed into run, like so:
[hostname] run: ls "/home/username/Folder Name With Spaces/"
With debug on, and assuming you’ve left shell set to True, you will see the literal, full string as passed to the remote server:
[hostname] run: /bin/bash -l -c "ls \"/home/username/Folder Name With Spaces\""
Enabling debug output will also display full Python tracebacks during aborts.
Where modifying other pieces of output (such as in the above example where it modifies the ‘running’ line to show the shell and any escape characters), this setting takes precedence over the others; so if running is False but debug is True, you will still be shown the ‘running’ line in its debugging form.
Changed in version 1.0: Debug output now includes full Python tracebacks during aborts.
In addition to the atomic/standalone levels above, Fabric also provides a couple of convenience aliases which map to multiple other levels. These may be referenced anywhere the other levels are referenced, and will effectively toggle all of the levels they are mapped to.
Changed in version 1.4: Added the commands output alias.
You may toggle any of Fabric’s output levels in a number of ways; for examples, please see the API docs linked in each bullet point:
Direct modification of fabric.state.output: fabric.state.output is a dictionary subclass (similar to env) whose keys are the output level names, and whose values are either True (show that particular type of output) or False (hide it.)
fabric.state.output is the lowest-level implementation of output levels and is what Fabric’s internals reference when deciding whether or not to print their output.
Context managers: hide and show are twin context managers that take one or more output level names as strings, and either hide or show them within the wrapped block. As with Fabric’s other context managers, the prior values are restored when the block exits.
Command-line arguments: You may use the --hide and/or --show arguments to fab options and arguments, which behave exactly like the context managers of the same names (but are, naturally, globally applied) and take comma-separated strings as input.