NAME

rerun - Take your shell scripts and turn them into powerful full featured management utilities with no extra programming.

SYNOPSYS

rerun [-h][-v][-V][--version] [-M <dir>] [module:[command [options]]]

DESCRIPTION

You are never going to get rid of bash scripts entirely. Rerun creates a nice interface for users and a framework for the scripters that makes you look good and a better team player.

Rerun is a simple command runner that turns loose shell scripts into modular automation. Rerun will help you organize your implementation into well defined command interfaces. Collections of management modules can be archived and delivered as a single executable to facilitate team hand offs. Using the "stubbs" module, rerun will even facilitate developing modules using a test-driven development practice.

What does rerun give you?

• A framework to script writing that does things like generate option parsers
• Command completion in your bash shell
• Packaging in rpm/deb or standalone
• Logging formats with levels and ansi color
• Nice user experience
• Simple to use test framework
• Build process you can hook into your CI loop

Rerun provides two modes of operation:

1. Listing: Rerun lists modules and commands. Listing information includes name, description and command line usage syntax.
2. Execution: Rerun provides option processing (possibly defaulting unspecified arguments) and executes a script for the specified module command.

For the module developer, rerun is a trivial framework following simple conventions that easily fit in a shell environment. Rerun includes a module development tool called "stubbs" that helps create and evolve rerun modules. Stubbs contains commands to automate option processing code, metadata definition and unit testing.

Internally, rerun implements a simple dispatching mechanism to look up named commands and execute them. Commands are logically named and have a corresponding script.

Commands reside in a module and can have named parameters called options. Each option is named, described and can also be defined to use a default value or say whether it is required or not.

Rerun modules can also declare metadata describing name, description and other aspects of each command. Rerun makes use of this metadata to support a listing mode, a feature where modules and command usage are summarized for end users.

See the project wiki for additional documentation including:

• Installation
• Tutorial
• Stubbs module tool
• Why rerun?
• Tutorial

OPTIONS

-h : Print help and usage then exit.

-M DIRECTORY : Module library directory path.

-v : Execute command in verbose mode.

-V : Execute rerun and command in verbose mode.

--version : Print the rerun version.

USING

Help

For command line syntax and example usage execute rerun using the --help flag:

$ ./rerun --help
 _ __ ___ _ __ _   _ _ __
| '__/ _ \ '__| | | | '_ \ 
| | |  __/ |  | |_| | | | |
|_|  \___|_|   \__,_|_| |_|
Version: v0.1. License: Apache 2.0.

Usage: rerun [-h][-v][-V][--version] [-M <dir>] [module:[command [options]]]

Examples:
| $ rerun 
| => List all modules.
| $ rerun waitfor
| => List all waitfor commands.
| $ rerun waitfor:http --url http://google.com
| => Execute the waitfor:http command.
| $ rerun -M /var/rerun waitfor:http
| => Execute the waitfor:http command found in /var/rerun

Listing

Without arguments, rerun will list existing modules:

$ rerun
  waitfor: "wait for condition."

To list the commands available from the 'waitfor' module:

$ rerun waitfor
http: "wait for url to become available"
    --url <>: "the url to check"
    --interval <30>: "the time interval"
ping: "wait for ping response from host"
    --host <"">: "host to check"
    --interval <30>: "the time interval"

The listing consists of info about command options including default values if they were described with option metadata.

Options that declare a default value are shown with a string between the "<>" characters.

For example, notice how "--interval" option shows <30>. The "30" is the default value assigned to the "--interval" option.

See the "Environment" section below to learn about the RERUN_MODULES environment variable. This variable specifies the directory where rerun modules exist.

Bash completion

If you are a Bash shell user, be sure to source the bash_completion.sh file. It provides listing via the tab key.

Type rerun and then the tab key. The shell will generate a list of existing modules.

$ rerun[TAB][TAB]
waitfor

Rerun shows there is a module named "waitfor" installed.

Typing the tab key again will show the commands inside the "waitfor" module:

$ rerun waitfor: [TAB]
http ping

In this case, two commands are found and listed. Press tab again and choose a command. After accepting a command, typing the tab key will show arguments.

$ rerun waitfor:ping -[TAB]
--host      --interval  

The waitfor:ping command accepts options (--host <> --interval <>).

Command execution

Commands are executed by stating the module, command and possibly options. The basic usage form is "rerun module:command [options]".

To run the "ping" command in the waitfor module, type:

$ rerun waitfor:ping --host localhost
OK: localhost is pingable.

The outputed string "OK: localhost is pingable." is the printed result. In this example, "30" is the interval option's default value as defined in the module metadata.

Command options are passed after the "module:command" string. Tell waitfor to wait for the url, "http://google.com" by specifying the --url <> option:

$ rerun waitfor:http --url http://google.com
OK

If the 'waitfor' module is stored in /var/rerun, then the command usage would be:

$ rerun -M /var/rerun waitfor:ping
OK: localhost is pingable.

Archives

An archive contains all the rerun modules you need (you might have a library of them) and gives you the same exact interface as rerun,... all in one file!

Specifically, an archive is a set of modules and rerun itself packaged into a self extracting script (by default in a file named "rerun.sh"). Archives can be useful if you want to share a single self contained executable that contains all the needed modules.

Run an archive script like you would run rerun.

You can execute an archive via bash like so:

$ bash rerun.sh <module>:<command> --your options

If the execute bit is set, invoke the archive directly.

Here the archive is executed without arguments which causes the archive to list the modules contained within it.

$ ./rerun.sh
  waitfor: "wait for a condition" - 1.0.0
  .
  . listing output ommitted

Note, ".sh" is just a suffix naming convention for a self-extracting script. The archive file can be named anything you wish.

Run the waitfor:http command in the archive:

$ ./rerun.sh waitfor:http --url http://google.com
.
.

See stubbs:archive for further information about creating and understanding rerun archives.

MODULES

Layout

A rerun module assumes the following structure:

<MODULE>
├── commands
│   ├── cmdA (directory for cmdA files)
│   │   ├── metadata (command metadata)
│   │   ├── script (command script)
│   │   └── options.sh (option parsing script)
│   └── cmdB
│       ├── metadata
│       ├── script 
│       └── options.sh
├── metadata (module metadata)
└── lib

Command Scripts

Rerun's internal dispatch logic uses the directory layout described above to find and execute scripts for each command.

Metadata

The metadata file format uses line separated KEY=value pairs to define module attributes. The module metadata file declares two properties:

• NAME: Declare name displayed to user.
• DESCRIPTION: Brief explanation of use.

For example, a module named waitfor is named and described in a file called RERUN_MODULES/waitfor/metadata:

NAME="waitfor"
DESCRIPTION="wait for a condition"

Command metadata is described in a file called RERUN_MODULES/<module>/commands/<command>/metadata. Here's the command metadata for the "ping" command:

NAME="ping"
DESCRIPTION="wait for ping response from host"

Options are described in a file called RERUN_MODULES/<module>/options/<option>/metadata. Beyond just NAME and DESCRIPTION, options can also declare:

• ARGUMENTS: Does the option take an argument.
• REQUIRED: Is the option required.
• DEFAULT: Sensible value for an option default

Here's the metadata describing the option named "host":

NAME=host
DESCRIPTION="the host to ping"
ARGUMENTS=true
REQUIRED=true
DEFAULT=

And for the --interval option

NAME=interval
DESCRIPTION="the interval to wait in seconds"
ARGUMENTS=true
REQUIRED=true
DEFAULT=30

Combining the examples above into the layout described earlier the "waitfor" module along with its commands "http" and "ping" are illustrated here:

waitfor
├── commands
│   └── http (directory for http command files)
│       ├── metadata (command metadata)
│       ├── options.sh (option parsing script)
│       └── script (command script)
├── lib
│   └── functions.sh (module function library)
├── metadata (module metadata)
├── options (module options)
│   ├── url (--url option)
│   │   └── metadata (declares metadata for "url" option)
│   └── interval (--interval option)
│       └── metadata (declares metadata for "interval" option)
└── tests
    └── http-1-test.sh (unit tests for http)

ENVIRONMENT

RERUN_MODULES : Path to directory containing rerun modules. If RERUN_MODULES is not set, it is defaulted relative to the location of the rerun executable.

RERUN_COLOR : Set 'true' if you want ANSI text effects. Makes labels in text to print bold in the console. Syntax errors will also print bold.

SEE ALSO

To create modules, see stubbs.

ERROR CODE

0 : All commands executed successfully

1 : One or more commands failed

127 : Unknown error case

LICENSE

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

The rerun source code and all documentation may be downloaded from https://github.com/rerun/rerun/.