govern

Linux process governor: a simple shell script to manage multiple processes

What govern.sh is

This shell script manages multiple processes defined in the configuration files located at ~/local/*.conf.sh. The shell script has released as an open source software and is publicly accessible on GitHub.

This govern.sh script can be executed from ether an interactive shell or through a cron job. Here's how you would initiate it from a cron job:

$ crontab -e
@reboot cd /home/pi/bin; ./govern.sh start

Repository Overview for New Contributors

Structure

• govern.sh – central Bash script that starts, stops, and checks the status of processes.
• local/*.conf.sh – configuration files describing each process via CMD, ARGS, and MARK.
• README.md – documentation including usage, testing, and licensing information.

Important Notes

• govern.sh expects the ~/local directory to exist and exits if it is missing.
• Run govern.sh start to launch all processes, stop to halt them, and status or no argument to view their state.
• Arguments containing spaces cannot be passed as a single string through environment variables; consider quoting or extending the script when needed.

Suggested Next Steps

1. Study local/sample.conf.sh and create your own configuration, ensuring the MARK uniquely identifies each process.
2. Trace functions such as get_pid and do_cmd in govern.sh to understand how process management works.
3. Explore ways to handle arguments with spaces—advanced quoting techniques or script enhancements may be required.
4. Try automating execution, for example with a cron entry using @reboot.

Usage

To initiate all processes specified in the ~/local/ directory, enter govern.sh start. The name and process ID (PID) of each process will be displayed.

To terminate all processes, type govern.sh stop.

To view the status of processes, type govern.sh status. Alternatively, you can simply enter govern.sh to list status and PID of all processes, as show below:

pi@rpi3b:~ $ govern.sh
clas.conf.sh running at pid 30185
f9p.conf.sh running at pid 2879
lora.conf.sh running at pid 450
madoca.conf.sh running at pid 455
sf9p.conf.sh running at pid 2897
pi@rpi3b:~ $

If you want to start, stop, or display a specific process, for example, use govern.sh sample.conf.sh start to initiate the process defined in sample.conf.sh.

The configuration file necessitates the definition of environment variables of CMD, ARGS, and MARK. ARGS must be declared using Bash array syntax (ARGS=(...)) so that each parameter is passed separately. Because this syntax is specific to Bash, both govern.sh and its configuration files must be executed with Bash; POSIX sh does not support arrays. This approach allows arguments containing spaces to be quoted individually. For example:

MARK="serial://ttyF9P:230400"
CMD=$HOME/exec/str2str
ARGS=(-in "$MARK" -a "JAVGRANT_G5T NONE" -out "tcpsvr://:$LPORT" -b 1)

Here ARGS is a Bash array, so ensure you invoke the script with Bash rather than sh.

When this configuration is loaded, govern.sh executes $CMD" "${ARGS[@]}, ensuring that JAVGRANT_G5T NONE is treated as a single argument. For further details, please refer to local/sample.conf.sh.

Testing

Run the test suite with Bats:

bats tests/

License

govern.sh is released under 2-Cluse BSD License.
Copyright (c) 2023 Satoshi Takahashi, all rights reserved.