Purpose

The sysexecute python package allows the easier execution of system tasks. Part of this is an auto-formatting mechanism for variable substitution, part of this is being able to simply specify the execution options.

Installation

You can install sysexecute from PyPi via pip:

pip install sysexecute

Variable Substitution

Typically in python to format a string we might do something like:

val = 3
print("the value of val is {val}".format(val=val))

This is kind of long and redundant. If we already have a value for val then it should be able to just be substituted. In fact if we do

from sysexecute import *
val = 3
print (stringWithVars("the value of val is {val}"))

The bindings for the variables follow normal python scoping rules. This makes the execution statements a good bit more readable.

Execution

Here is a typical execution

execute("ssh {machineIP} ls {thePath}")

assuming the variable machineIP and thePath have values. The normal output of this script gets piped to StdOut and StdErr, but if you want to capture these you can with something like:

(rc, stdout, stderr) = execute("ssh {machineIP} ls {thePath}", captureStdOutStdErr=True)

There are various keyword options you can specify like:

• cwd : change the directory from which the command will be executed
• ignoreErrors: Unless this is true a sys.exit(returnCode) will be issued if there is a non-zero return code.
• shell: if a shell should be used (defaults to True)
• executable: which shell to use (defaults to /bin/bash)
• colorize: wether to colorize the output (defaults to True)
• dryRun : print what would be executed but don't actually execute anything

Verbosity

Often in scripting we want to include debugging / info commentary depending on what level of verbosity we are requested to display. You can set the level of verbosity shown via eg:

set_execute_defaults('verbosity',2)

Then in the following only the first two strings would be printed:

printWithVars1("success!")
printWithVars2("Machine {machineIP} was reached.")
printWithVars3("You might want to check that blah and blah.")

Testing

To run the test suite you need py.test installed on your machine. Then you can simply execute:

cd tests
py.test