Scripting¶
Operating system shells have long had the ability to execute a sequence of
commands saved in a text file. These script files make long sequences of
commands easier to repeatedly execute. cmd2
supports two similar
mechanisms: command scripts and python scripts.
Command Scripts¶
A command script contains a sequence of commands typed at the the prompt of a
cmd2
based application. Unlike operating system shell scripts, command
scripts can’t contain logic or loops.
Creating Command Scripts¶
Command scripts can be created in several ways:
- creating a text file using any method of your choice
- using the built-in edit command to create or edit an existing text file
- saving previously entered commands to a script file using history -s
If you create create a text file from scratch, just include one command per
line, exactly as you would type it inside a cmd2
application.
Running Command Scripts¶
Command script files can be executed using the built-in
run_script command or the @
shortcut (if
your application is using the default shortcuts). Both ASCII and UTF-8 encoded
unicode text files are supported. The
run_script command supports tab completion of
file system paths. There is a variant
_relative_run_script command or @@
shortcut (if using the default shortcuts) for use within a script which uses
paths relative to the first script.
Comments¶
Any command line input where the first non-whitespace character is a # will be treated as a comment. This means any # character appearing later in the command will be treated as a literal. The same applies to a # in the middle of a multiline command, even if it is the first character on a line.
Comments are useful in scripts, but would be pointless within an interactive session.
(Cmd) # this is a comment
(Cmd) command # this is not a comment
Python Scripts¶
If you require logic flow, loops, branching, or other advanced features, you
can write a python script which executes in the context of your cmd2
app.
This script is run using the run_pyscript
command. Here’s a simple example that uses the arg_printer script:
(Cmd) run_pyscript examples/scripts/arg_printer.py foo bar 'baz 23'
Running Python script 'arg_printer.py' which was called with 3 arguments
arg 1: 'foo'
arg 2: 'bar'
arg 3: 'baz 23'
run_pyscript supports tab completion of file system paths, and as shown above it has the ability to pass command-line arguments to the scripts invoked.
Python scripts executed with run_pyscript can
run cmd2
application commands by using the syntax:
app(‘command args’)
where:
app
is a configurable name which can be changed by setting thecmd2.Cmd.py_bridge_name
attributecommand
andargs
are entered exactly like they would be entered by a user of your application.
See python_scripting example and associated conditional script for more information.
Advanced Support¶
When implementing a command, setting self.last_result
allows for application-specific
data to be returned to a python script from the command. This can allow python scripts to
make decisions based on the result of previous application commands.
The application command (default: app
) returns a cmd2.CommandResult
for each command.
The cmd2.CommandResult
object provides the captured output to stdout
and stderr
while a command is executing. Additionally, it provides the value that command stored in
self.last_result
.
Additionally, an external test Mixin plugin has been provided to allow for python based external testing of the application. For example, for system integration tests scenarios where the python application is a component of a larger suite of tools and components. This interface allows python based tests to call commands and validate results as part of a larger test suite. See External Test Plugin