scanwatch

summary

simple utility to watch a directory and forward any new pdf file within to a printing frontend (linux only!)

This software is developed for my own personal use. However, if you have suggestions, feel free to contact me.

use cases

• watch scanner directory for new files and forward them to the printer
• watch scanner directory for new files and open them in pdf viewer
• watch download directory for new files with a certain name and move them to a certain folder

features

• execute multiple actions when a new file is created
• display notification upon action (with custom icon)
• path can include '~' for user home directory

limitations

• Linux only
• It is not possible to watch SMB mounted paths (i.e. Windows Shares), because the underlying linux notification library (inotify) does not support it.
• Only one path (and its subdirectories) can be watched. Originally I had intended to specify the path for each rule, but the current implementation was much easier.

configuration

Example configuration file:

path ="~/scanwatch"

[rules.pdf]
ends_with = ".pdf"
cmd = "xdg-open"
args = ["{filename}"]
icon = "application-pdf"
msg = "opening '{filename:short}' with default viewer"

[rules.lpr]
starts_with = "CN"
ends_with = ".pdf"
x = "kyo_einseitig"
cmd = "lpr"
args = ["-P{x}", "{filename}"]
msg = "sending '{filename:short}' to printer '{x}'"
icon = "printer"

Valid variables:

scope	mandatory/optional	variable	meaning	examples
global	mandatory	path	path to watch (including subdirectories)	"~/scanwatch", "scanwatch", "/home/foo//scanwatch"
rules	mandatory	cmd	command to execute if watched file matches rule	"xdg-open", "lpr"
rules	mandatory	args	list of arguments to pass to the given command	["-P{x}"], ["--verbose"]
rules	mandatory	msg	message to display in the notification	"sending {filename} to default viewer"
rules	optional	starts_with	beginning of file name (without watched path)	"CN_"
rules	optional	ends_with	end of file name (without watched path)	".pdf", ".zip"
rules	optional	filter	filter expression (rust regular expression)	"\\.pdf$", "^CN.*"
rules	optional	x, y, z	optional variables that can be used in the args variable	"anything"
rules	optional	icon	name of icon to display	"application-pdf", "printer"

Args and msg can contain the following placeholder variables:

placeholder	expansion to
{filename}	matched filename (complete path)
{filename:short}	matched filename (without watched path prefix)
{x}, {y}, {z}	rule variable 'x', 'y' or 'z'

internal workflow

• look for configuration file 'scanwatch.toml', either from the current directory or from the XDG home configuration directory (usually ~/.config/scanwatch/scanwatch.toml)
• read global watch path from config file
• read action rules from config file
• watch path for new file creation using inotify
• upon new file creation or existing file write:
• display message using desktop notification
• execute the command that is given by the matching rule, e.g. lpr -P{printer-name} {document-name} for every file that matches the above rule

future plans

• add proper meta information, update version number
• add fancy app logo
• optional audio bell
• add command line options (help, verbose, location of config file)

disclaimer

Of course, it would have been much easier to write this using a shell script. But rust is so great, I wanted to play with it and maybe I will enhance this a little more later on...