Adding Bash Dependencies to an Electron

Bash dependencies can be passed to an electron as an argument to the electron decorator. The dependencies can take one of two forms:

1. A Covalent DepsBash object.
2. A list of commands represented as strings.

Both forms are illustrated below.

Prerequisites

Import covalent.

import covalent as ct

Procedure

Using a Covalent DepsBash object

1. Pass a comma-separated list of Bash commands to the constructor of a DepsBash() object, then assign the object to the deps_bash keyword argument:

@ct.electron(
        deps_bash=ct.DepsBash(["echo `whereis cpp` > /tmp/path.txt"]),
)
def get_bash_result():
    with open('/tmp/path.txt','r') as f:
        return f.read()

2. Use the electron in a lattice and dispatch the lattice as usual:

@ct.lattice
def workflow():
    return get_bash_result()

dispatch_id = ct.dispatch(workflow)()
r = ct.get_result(dispatch_id, wait=True)
print(r.result)

cpp: /usr/bin/cpp

Using a List

1. Pass a list of commands – represented as strings – directly to the deps_bash named argument:

@ct.electron(
        deps_bash=["echo `whereis cpp` /tmp/path.txt"],
)
def get_bash_result():
    with open('/tmp/path.txt','r') as f:
        return f.read()

2. Dispatch the elctron in a lattice as usual:

@ct.lattice
def workflow():
    return get_bash_result()

dispatch_id = ct.dispatch(workflow)()
r = ct.get_result(dispatch_id, wait=True)
print(r.result)

cpp: /usr/bin/cpp

See Also

Constructing Tasks from Bash Scripts