===== Let 'diff' Ignore Certain Text Lines =====

When an ''ICS'' file is downloaded repeatedly from a ''CALDAV'' server, e.g. using ''wget'' or ''curl'', then the ''DTSTAMP'' property
in each ''VEVENT'' is likely to be set zo the current download date, even though the events themselves haven't changed.
So a simple ''diff'' against a previous version of the file might yield lots of differences even though no event has really changed.

To ignore the ''DTSTAMP''-only changes ''diff'' can be called to ignore all lines starting with ''DTSTAMP:'' when comparing
the newly downloaded file to an older version of the same file:

<code>
diff -Naur -I ^DTSTAMP:.* file_new.ics file_old.ics; echo $?
</code>

The example above also prints the return code from ''diff'' which could be evaluated in a scipt to check if further actions are required, or not.

----

 --- //Martin Burnicki [[martin.burnicki@burnicki.net]] 2019-03-06//