How can I pass a parameter to a fabric task when calling “fab” from the command line? For example:

def task(something=''):
    print "You said %s" % something

$ fab task "hello"
You said hello

Done.

Is it possible to do this without prompting with fabric.operations.prompt?

Fabric 2 task arguments documentation:

http://docs.pyinvoke.org/en/latest/concepts/invoking-tasks.html#task-command-line-arguments

Fabric 1.X uses the following syntax for passing arguments to tasks:

 fab task:'hello world'
 fab task:something='hello'
 fab task:foo=99,bar=True
 fab task:foo,bar

You can read more about it in Fabric docs.

Fabric arguments are understood with very basic string parsing, so you have to be a bit careful with how you send them.

Here are a few examples of different ways to pass arguments to the following test function:

@task
def test(*args, **kwargs):
    print("args:", args)
    print("named args:", kwargs)

$ fab "test:hello world"
('args:', ('hello world',))
('named args:', {})

$ fab "test:hello,world"
('args:', ('hello', 'world'))
('named args:', {})

$ fab "test:message=hello world"
('args:', ())
('named args:', {'message': 'hello world'})

$ fab "test:message=message \= hello\, world"
('args:', ())
('named args:', {'message': 'message = hello, world'})

I use double quote here to take the shell out of the equation, but single quotes may be better for some platforms. Also note the escapes for characters that fabric considers delimiters.

More details in the docs: http://docs.fabfile.org/en/1.14/usage/fab.html#per-task-arguments

In Fabric 2, simply add the argument to your task function. For example, to pass the version argument to task deploy:

@task
def deploy(context, version):
    ...

Run it as follows:

fab -H host deploy --version v1.2.3

Fabric even documents the options automatically:

$ fab --help deploy
Usage: fab [--core-opts] deploy [--options] [other tasks here ...]

Docstring:
  none

Options:
  -v STRING, --version=STRING

You need to pass all Python variables as strings, especially if you are using sub-process to run the scripts, or you will get an error. You will need to convert the variables back to int/boolean types separately.

def print_this(var):
    print str(var)

fab print_this:'hello world'
fab print_this='hello'
fab print_this:'99'
fab print_this='True'

If someone is looking to pass parameters from one task to another in fabric2, just use the environment dictionary for that:

@task
def qa(ctx):
  ctx.config.run.env['counter'] = 22
  ctx.config.run.env['conn'] = Connection('qa_host')

@task
def sign(ctx):
  print(ctx.config.run.env['counter'])
  conn = ctx.config.run.env['conn']
  conn.run('touch mike_was_here.txt')

And run:

fab2 qa sign