NAME

rerun - a simple command runner because it's easy to forget standard operating procedure.

SYNOPSYS

rerun [-h][-v][-V] [-M <dir>] [-L <dir>] [--replay <file>] [module:[command [options]]]

DESCRIPTION

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 unit tests. When users execute rerun module commands, rerun can record execution data into log files that can later be replayed.

Rerun provides two modes of operation:

Listing: Rerun lists modules and commands. Listing information includes name, description and command line usage syntax.
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:

OPTIONS

-h : Print help and usage then exit.

-M DIRECTORY : Module library directory path.

-L DIRECTORY : Recorded command execution logs stored in this directory. Also settable via RERUN_LOGS.

--replay *LOG* : Compare the results of a command execution to that in a replay log and show the difference in output if any.

-v : Execute command in verbose mode.

-V : Execute rerun and command in verbose mode.

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] [-M <dir>] [-L <dir>] [--replay <file>] [module:[command [command_args]]]

Examples:
| $ rerun 
| => List all modules.
| $ rerun freddy
| => List all freddy commands.
| $ rerun freddy:dance --jumps 3
| => Execute the freddy:dance command.
| $ rerun -M /var/rerun freddy:dance
| => Execute the freddy:dance command found in /var/rerun

Listing

Without arguments, rerun will list existing modules:

$ rerun
  freddy: "A dancer in a red beret and matching suspenders"

To list the commands available from the 'freddy' module run:

$ rerun freddy
 study: "tell freddy to study"
   --subject <math>: "the summer school subject"
 dance: "tell freddy to dance"
   --jumps <1>: "jump #num times"

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 "--jumps" option shows <1>. The "1" is the default value assigned to the "--jumps" 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]
freddy

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

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

$ rerun freddy: [TAB]
dance  study

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 freddy:study -[TAB]
--subject

The freddy:study command accepts one option (--subject <>).

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 "study" command in the freddy module, type:

$ rerun freddy:study
studying (math)

The outputed string "studying (math)" is the printed result. In this example, "math" is the subject option's default value as defined in the module metadata.

Command options are passed after the "module:command" string. Tell freddy to study the subject, "biology" by specifying the --subject <> option:

$ rerun freddy:study --subject biology
studying (biology)

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

$ rerun -M /var/rerun freddy:study
studying (math)

LOGS

Rerun records command execution as replay logs, if the -L <dir> argument is set or the RERUN_LOGS environment variable is set. Be sure to set RERUN_LOGS to a writable directory.

Each command execution is recorded in the form of a "replay" log file (ending with .replay). This log file contains information about the command execution, as well as, the output from the execution.

These .replay files can be edited or executed as scripts.

File naming

Each replay log is named using the following pattern:

$RERUN_LOGS/$MODULE-$COMMAND-YYYY-MM-DD-THHMMSS-PID.replay

To list the replay logs for the freddy:dance command use ls:

$ ls -l $RERUN_LOGS/freddy-dance*.replay
-rw-rw----  1 alexh  wheel  188 Sep 21 19:54 freddy-dance-2011-09-21T195402-2344.replay

File format

Replay logs follow a simple format that combines command execution metadata and log output.

Replay log metadata:

RERUN: The rerun executable
MODULE: The module name
COMMAND: The command name
OPTIONS: The command options
USER: The user executing the command
DATE: The timestamp for the execution

Here's the metadata as specified in the file template:

#
# Rerun replay log
#
RERUN="$RERUN"
MODULE="$MODULE"
COMMAND="$COMMAND"
OPTIONS="$*"
USER="$USER"
DATE="$(date '+%Y-%m%d-%H%M%S')"
__COMMAND_OUT_BELOW__

Any command output is stored below the line delimiter, __COMMAND_OUT_BELOW__.

Here's an example replay file for the freddy:dance command:

#
# Rerun replay log
#
RERUN="/Users/alexh/rerun-workspace/rerun/rerun"
MODULE="freddy"
COMMAND="dance"
OPTIONS=""
USER="alexh"
DATE="2011-0921-195402"
__COMMAND_OUT_BELOW__

jumps (1)

This simple shell function will parse the content for a given replay log:

rerun_extractLog() {
	[ -f $1 ] || die "file does not exist: $1"
	SIZE=$(awk '/^__COMMAND_OUT_BELOW__/ {print NR + 1; exit 0; }' $1) || die "failed sizing output"
	tail -n+$SIZE $1 || die "failed extracting output"
}

Running this shell function for a given replay log looks similar to this:

$ rerun_extractLog $RERUN_LOGS/freddy-dance-2011-0921-194512.replay

jumps (1)

Replay

Rerun supports basic command replay logging (See "Logs" section below). When rerun logs a command it does so in a form that can be re-executed (i.e., "replayed"). It's possible to have rerun compare the results of a given replay log against a new command execution. Replay logs are normally found in the directory specified by the RERUN_LOGS environment variable (or the -L <dir> option).

Use the --replay <log> option to compare replay output from a command log.

Below you can see the results of a comparison between this run of freddy:dance --jumps 2 against an earlier command execution. After the command completes, rerun uses the diff command to compare the log output.

$ ./rerun --replay $RERUN_LOGS/freddy-dance-2011-09-21T140744.replay freddy:dance --jumps 2
jumps (2)
[diff]
2c2
< jumps ()
---
> jumps (2)

In this case, the replay contained "jumps ()" while the new execution printed "jumps (2)". When a difference is detected, rerun will print the differences below the [diff] label and exit with a non-zero exit status.

MODULES

Layout

A rerun module assumes the following structure:

<MODULE>
├── commands
│   ├── cmdA (directory for cmdA files)
│   │   ├── metadata (command metadata)
│   │   ├── default.sh (generic script)
│   │   ├── optX.option (declares metadata for "optX" option)
│   │   └── options.sh (option parsing script)
│   └── cmdB
│       ├── Darwin.sh (OS specific script)
│       ├── metadata
│       ├── default.sh (generic script)
│       ├── options.sh
│       └── optY.option (declares metadata for "optY" option)
├── 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.

Rerun expects a default implementation script for each command but can also invoke an OS specific script, if present.

default.sh: Generic implementation.
$(uname -s).sh: OS specific implementation
options.sh: Script sourceable by default and OS specific scripts to parse options (also generated by stubbs).

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 freddy is named and described in a file called RERUN_MODULES/freddy/metadata:

NAME="freddy"
DESCRIPTION="A dancer in a red beret and matching suspenders"

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

NAME="study"
DESCRIPTION="tell freddy to study"

Options are described in a file called RERUN_MODULES/<module>/commands/<command>/<option>.option. 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 subject.option describing an option named "subject":

NAME=subject
DESCRIPTION="the summer school subject"
ARGUMENTS=true
REQUIRED=true
DEFAULT=math

Combining the examples above into the layout described earlier the "freddy" module along with its commands "dance" and "study" are illustrated here:

freddy
├── commands
│   ├── dance
│   │   ├── metadata
│   │   ├── default.sh
│   │   ├── jumps.option
│   │   └── options.sh
│   └── study
│       ├── metadata
│       ├── default.sh
│       ├── options.sh
│       └── subject.option
├── metadata
└── lib

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_LOGS : Path to directory where rerun will record command executions as replay log files.

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.

DIFF : Set to the particular diff command to use for replay log comparisons.

ERROR CODE

0 : All commands executed successfully.

1 : One or more commands failed.

2 : Option error.

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/.

heim / rerun