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run-parts

run-parts is a command-line utility in Unix-like operating systems that executes all executables located in a specified directory.

It's used by cron to run scheduled tasks (e.g., /etc/cron.daily, /etc/cron.hourly, etc.) and can be used in other contexts where we want to execute a series of scripts or programs.

Although it's primarily a system utility, it can also be used manually or in scripts.

Usage

The basic syntax for run-parts is:

run-parts [options] <directory>
The <directory> specifies the directory where the executables are located.

By default, run-parts executes the files in alphabetical order. This includes numeric prefixes, so files named 01-backup, 02-cleanup, etc., will be executed in that order.

Note on Filenames

run-parts will only execute files that are executable and do not contain a dot (.) in their names.
So, for example, a file named backup.sh would not be executed by run-parts, but a file named backup would be executed, provided it has executable permissions.

Options

There are many options/flags available for run-parts that control its behavior.

Some useful options:

  • --test: Only print the names of the executables that would be run, without actually executing them.

    • This is essentially a dry run mode.

  • --list: Print the names of all matching files, including those without execute permissions.

    • Can be used with --regex to filter the list of files based on a regex pattern.

  • --debug: Print which scripts are selected for execution and which are not.

    • Outputs to stderr.
    • This does execute the scripts, but provides additional information about the selection process.

  • --exit-on-error: Cause run-parts to exit immediately if any of the executables return a non-zero exit status.

    • Useful for ensuring that if any script fails, the entire process stops, making it an atomic operation.

  • --verbose: Print the name of each executable as it is run.

  • --regex=RE: Only run executables whose names match the regex pattern RE.

    • Allows us to filter which executables are run based on their names.
    • This option accepts Extended Regular Expressions (EREs).

Examples

  • To run all executables in the /etc/cron.daily directory, we would use: 

    run-parts /etc/cron.daily
    This command will execute all the executables in the /etc/cron.daily directory, except those containing a dot in the filename.

  • To see which executables would be run without actually executing them, we can use: 

    run-parts --test /etc/cron.daily

  • To only show a list all files that will be executed and which will be skipped, we can use: 

    run-parts --debug --list /etc/cron.daily
    This will print all the files that will be run and which will be skipped, along with the reason for skipping (e.g., not executable, contains a dot). The reason will be "classicalre fail" if the file is skipped because it contains a dot or is not executable.