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--- bash:directories:monitor_a_directory_for_changes:using_incron [2022/06/13 09:14] – created peter
+++ bash:directories:monitor_a_directory_for_changes:using_incron [2022/06/13 09:18] (current) – peter
@@ Line 1: / Line 1: @@
 ====== BASH - Directories - Monitor a directory for changes - Using incron ======
+**incron** is like cron but instead of time-based events, the events are based on file notifications.
+----
+===== Install incron =====
+<code bash>
+sudo apt install incron
+</code>
+----
+===== Change Permissions =====
+Add users to the **/etc/incron.allow** file who are allowed to use incron.
+<file bash /etc/incron.allow>
+peter
+</file>
+<WRAP info>
+**NOTE:**  One user per line.
+**/etc/incron.deny** can also be used to specifically prevent usage of incron by a user.
+</WRAP>
+----
+===== Monitor =====
+Edit the incron table:
+<code bash>
+incrontab -e
+</code>
+and populate with:
+<code>
+/etc/apache2/apache2.conf IN_MODIFY /usr/sbin/service apache2 stop
+/home/peter/some_dir_to_watch IN_MODIFY echo "$$ $@ $# $% $&"
+</code>
+<WRAP info>
+**NOTE:**  This monitors the directory for changes and will perform the echo passing along some parameters.
+The format is very picky; use spaces, not tabs!
+  * The format is **path mask command**.
+Parameters can include:
+  * **$$**:  Prints a dollar sign.
+  * **$@**:  The watched filesystem path.
+  * **$#**:  The event-related file name.
+  * **$%**:  The event flags/time (textually).
+  * **$&**:  The event flags.time (numerically).
+Events to monitor include:
+  * **IN_ACCESS**:  If a file is accessed or read.
+  * **IN_ATTRIB**:  If metadata of a file change (e.g. timestamps, permissions).
+  * **IN_CLOSE_WRITE**:  If a file opened for writing is closed.
+  * **IN_CLOSE_NOWRITE**:  If a file or directory not opened for writing is closed.
+  * **IN_CREATE**:  If a file or directory is created in a watched directory.
+  * **IN_DELETE**:  If a file or directory is deleted from a watched directory.
+  * **IN_DELETE_SELF**:  If a watched file or directory is deleted (or moved to a different filesystem).
+  * **IN_MODIFY**:  If a file was modified.
+  * **IN_MOVE_SELF**:  If a watched file or directory is moved within the filesystem.
+  * **IN_MOVED_FROM**:  If a file or directory is moved out of the watched directory.
+  * **IN_MOVED_TO**:  A file or directory is moved to the watched directory.
+  * **IN_OPEN**:  A watched file or directory is opened.
+</WRAP>
+<WRAP important>
+**IMPORTANT:**  incron is not capable of watching sub-directories.
+Only files within the path will be monitored.
+If sub-directories need to be monitored, they must be given their own entry.
+</WRAP>
+----
+===== List the incron table =====
+<code bash>
+incrontab -l
+</code>