Welcome!

fswait is a utility for blocking on the observation of a filesystem event for a path with a timeout.

This is useful when you need to block the execution of a separate program on the creation (or some other filesystem event) of a filepath but you want that block constrained by a timeout.

A common use-case is in systemd services, some daemons may need a socket or some other file to exist before starting and it is common to write shell code to implement that check-and-wait-with-timeout.

This tool makes that pattern more easily expressed as a command line utility call that also supports observing many different filesystem events for the specified path.

$ fswait --path /etc/someconfig.ini --modify --create && echo 'Do something!'
observing Create Modify for /home/parnell/Desktop/test.sh
the window for an observation is 120s
Created {isDirectory = False, filePath = "someconfig.ini"}
Do something!

When an observation occurs, the utility will return immediately with an exit code of 0 and print the observed event.

If the timeout window is reached without an observation occurring, an exit code of 1 is returned.

$ fswait --help
Wait and observe events on the filesystem for a path, with a timeout

Usage: fswait [--timeout Seconds] --path FILEPATH [--exists] (--access |
              --modify | --attrib | --close | --closeWrite | --closeNoWrite |
              --open | --move | --moveIn | --moveOut | --moveSelf | --create |
              --delete | --onlyDir | --noSymlink | --maskAdd | --oneShot |
              --all) ([--access]... | [--modify]... | [--attrib]... |
              [--close]... | [--closeWrite]... | [--closeNoWrite]... |
              [--open]... | [--move]... | [--moveIn]... | [--moveOut]... |
              [--moveSelf]... | [--create]... | [--delete]... | [--onlyDir]... |
              [--noSymlink]... | [--maskAdd]... | [--oneShot]... | [--all]...)

Available options:
  -h,--help                Show this help text
  --timeout Seconds        Window to observe a filesystem event (default: 120s,
                           negative values wait indefinitely)
  --path FILEPATH          Observe filesystem events for path
  --exists                 Return immediately if the filepath already exists

Installing

If you have Nix you can install it using:

$ nix-env --install --attr fswait release.nix