Notification script | from RSS to Email | Bash

Question

This is a script that must send an email at each new article published on a specific website. Any suggestions or improvements to do?

SENDER_EMAIL="[email protected]"
TO_EMAIL="[email protected]"
RSS_SITE="example.com/feed.xml"
CHECK_INTERVAL=10
while [ 1 ]; do
 LINK_ARTICLE=$(rsstail -i 1 -u $RSS_SITE -l -n 0 -1 | grep -oP "Link:+ \K.*")
 TITLE_ARTICLE=$(rsstail -i 1 -u $RSS_SITE -n 0 -1 | grep -oP "Title:+ \K.*")
 if [ "$LINK_ARTICLE" != "" ] && [ "$TITLE_ARTICLE" != "" ]; then
 echo "New article published on the site. TITLE: $TITLE_ARTICLE - LINK: $LINK_ARTICLE" | EMAIL="$SENDER_EMAIL" mutt -s "Nuovo Articolo BDO" "$TO_EMAIL"
 echo "New article published on the site. TITLE: $TITLE_ARTICLE - LINK: $LINK_ARTICLE"
 fi
 sleep $CHECK_INTERVAL
done

Answer 1

I see a number of things that may help you improve your code.

Use "shebang" line

The shebang is the line at the beginning of a shell script that tells which program to use. In this case, you probably want this:

#! /usr/bin/env bash

See this question for details.

Consider using cron instead of sleep

If this is something you want to run automatically, consider running it as a cron tab instead of using sleep within the script.

Include some comments

The program requires rsstail, mutt and sleep which is a requirement that should be documented in a comment.

Be cautious about handing variables to programs

The mutt program, like many Linux programs, has a -- option which specifies that no further options are on the command line. This prevents the contents of $TO_EMAIL in a line like the following from being misinterpreted as a command line option.

mutt -s $TITLE -- $TO_EMAIL < $BODYTEXT

Combine strings

The echo is used twice with an identical string. An alternative approach is

TITLE="Nuovo Articolo BDO"
BODYTEXT="New article published on the site. TITLE: $TITLE_ARTICLE - LINK: $LINK_ARTICLE"
mutt -s $TITLE -- $TO_EMAIL < $BODYTEXT
echo $BODYTEXT

Avoid creating extraneous variables

Instead of creating SENDER_EMAIL, you could just specify EMAIL and then the reassignment of the latter variable before mutt is called would not be necessary.

Consider writing a portable script

By sticking closely with Posix and avoiding bashisms your code could run on many different kinds of systems, including recent versions of Ubuntu which don't use bash.

• Alex Jones: Hi, thanks for your meticulously written answer. Can you please explain why you would consider cron job instead of sleep in this case? Thanks.
• Edward: One of the principles used in Linux is that programs are designed to do just one thing well. Because cron is a standard Linux tool to automatically run software on a periodic basis, I would probably use it for this application rather than having an infinitely running script.
• Alex Jones: I don't know about that. I think cron is just a bloat when I can do the same thing with while loop and sleep - using the same principle - use while loop to repeat stuff - use sleep to pause b/w execution.
• Edward: The odds are about 99.9% that your system is already running cron so I don't think it reasonably qualifies as bloat. In any case, the advice was merely to consider its use.