Pass parameter to fabric task

Question

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?

Jakub Roztocil · Accepted Answer · 2018-08-21T17:45:33.503

215

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.

edited Aug 21 '18 at 17:45

answered Jan 22 '12 at 12:00

Jakub Roztocil

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The quotes aren't necessary; all arguments are strings: "since this process involves string parsing, all values will end up as Python strings, so plan accordingly. (We hope to improve upon this in future versions of Fabric, provided an intuitive syntax can be found.)" – Carl G May 06 '14 at 15:39
4

The quotes around `hello world` seem necessary though? – PEZ Nov 11 '15 at 08:16
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@PEZ If that's true, quotes are probably necessary in that example because the terminal or fabric's command line parser would see the space and think that was the end of everything for that task and that `world` was a new task. – Adam Kerz Dec 23 '15 at 11:45
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Additionally, after using this for less than a minute, I've found that, on Windows, using single quotes results in the single quotes being passed as part of the argument, but double quotes are stripped first. So, `'hello world'` would result in a Python string of `'hello world'`, but `"hello world"` would result in `hello world` (which is probably what most people would want). – Adam Kerz Dec 23 '15 at 11:49
5

Since the process involves string parsing, `bar=True` in fabric command will passed as `bar='True'` which is not boolean value – Chemical Programmer Feb 16 '16 at 00:26

mrts · Answer 2 · 2019-03-09T16:33:43.910

14

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

edited Mar 09 '19 at 16:33

answered Mar 09 '19 at 12:21

mrts

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is there a way to predefine the hosts in the function itself? Similar to @roles() tag where we can define list of hosts to run the task. – Anish Sep 16 '19 at 20:43
define them in a list. – Coddy May 11 '21 at 02:24

score 7 · Answer 3 · edited Apr 01 '21 at 12:57

Fabric 1.x 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

score 2 · Answer 4 · edited Apr 17 '16 at 23:18

2

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'

edited Apr 17 '16 at 23:18

Misa Lazovic

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answered Apr 17 '16 at 23:02

frage

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score 2 · Answer 5 · answered Jan 30 '19 at 12:16

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

Pass parameter to fabric task

5 Answers5

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