What is cloe_run?

Simplifying, it is a tool for running any command in continous loop. cloe_run is a Continous Loop Execution tool. It has several other features such as:

• Finish the execution loop at the next iteration by sending a TERM signal.
• Suspending (pausing) the execution of the next loop until resumed.
• Loading environment variables from a set of predefined configuration files.
• Can be configured from .conf files and/or from environment variables.
• Executing commands before and/or after each loop main command.
• Doing a single execution by using a specific flag for debugging purposes.
• Logging command output (both STDOUT and STDERR) to a file.
• Customize the execution output's pipe command chain.
• Displaying execution status in screen terminal windows.
• Timestamping each output line using the ts tool (can be disabled).

Basic usage

Configuration of cloe_run is done via environment variables. Most, but not all of them begin with the CLOE_RUN_ prefix. The only required variable to run is CLOE_RUN_BIN, which designates the command you want to run in loop. Example:

$ CLOE_RUN_BIN="ls -lA" ./cloe_run

The above command line sets de required variable and launches cloe_run, which will start executing the ls -lA in continous loop until interrupted with CTRL+C.

Configuration file usage

You can create a configuration file with the desired configuration parameters and pass it to cloe_run as its first parameter. Create a file named test.conf with the content:

CLOE_RUN_BIN="ls -Al"
SLEEP=5s

After saving, invoke cloe_run like this:

$ ./cloe_run test

Note that you must omit the .conf extension, since it's added automatically. This will run the same command as before, with a 5 second sleep. The SLEEP parameter is passed directly to the sleep command, so it accepts the same values, such as 5s, 1m, 2h and so on. Check sleep manpage to find more.

Execution control

Suspension

There are times when you want to temporarily stop the loop from running. This is what cloe_run means by suspending a loop. This avoids you having to launch the script again when you no longer want it to be stopped, especially when there are lots of them. Also, this allows you to schedule suspension of all or some loops via crontab without needing to keep track of which loops are running to resume them later.

Suspension is triggered by creation of specific, predefined files in the directory specified via the CLOE_RUN_SUSPEND_DIR environment variable, which defaults to the current working dir (PWD). The file contents is irrelevant, they can be an empty file. There is a global suspension file and another, conf-file specific one. By default, the global suspension file is CLOE_RUN_SUSPEND_DIR/suspend.cloe_run, but the global suspend file name can be configured via the CLOE_RUN_SUSPEND_FILE environment variable. There is also a CLOE_RUN_SUSPEND_DIR/suspend.CLOE_RUN_CONF_NAME that will only match the configuration file name loops.

If cloe_run finds any suspension file, it will use the inotifywait program from the inotify-tools package, if present to wait for its deletion. If the package is not available, cloe_run will fall back to do a sleep for CLOE_RUN_SUSPEND_SLEEP parameter. The former method has instant resumption, since it doesn't needs the sleep to end to detect that the suspension file has been deleted.

The loop will resume as soon as the suspension file is no longer present.

Configuration parameters

TODO