A Web-Based Clipping Service
Now that we have a program to retrieve documents that fit our criteria, how can we use it? We could run it from the command line, but the point of this program is to do your work for you, downloading documents while you sleep or watch television.
The easiest way is to use cron, the Linux facility that allows us to run programs at regular intervals. Each user has his or her own crontab, a table that indicates when a program should be run. Each command is preceded by five columns that indicate the time and date on which a program should be run: the minute, hour, day of month, month and day of the week. These columns are normally filled with numbers, but an asterisk can be used to indicate a wild card.
The following entry in a crontab indicates the program /bin/foo should be run every Sunday at 4:05 A.M.:
5 4 * * 0 /bin/foo
Be sure to use a complete path name when using cron—here we indicated /bin/foo, rather than just “foo”.
The crontab is edited with the crontab program, using its -e option. This will open the editor defined in the EDITOR environment variable, which is vi by default. (Emacs users should consider setting this to emacsclient, which loads the file in an already running Emacs process.)
To download all of the files matching our phrases from Wired News every day at midnight, we could use the following:
0 0 * * 0 /usr/bin/download-matching.pl\ www.wired.com/news/http://www.wired.com/news/
This will start the process of downloading files from http://www.wirec.com/news/ at midnight, placing the results in $output_directory. We can specify multiple URLs as well, allowing us to retrieve news from more than one of our favorite news sources. When we wake up in the morning, new documents that interest us will be waiting for us to read, sitting in $output_directory.
Many organizations hire clipping services to find news that is of interest to them. With a bit of cleverness and heavy reliance on LWP, we can create our own personalized clipping service, downloading documents that reflect our personal interests. No longer must you look through a list of headlines in order to find relevant documents—let Perl and the Web do your work for you.
|PostgreSQL, the NoSQL Database||Jan 29, 2015|
|HPC Cluster Grant Accepting Applications!||Jan 28, 2015|
|Sharing Admin Privileges for Many Hosts Securely||Jan 28, 2015|
|Red Hat Enterprise Linux 7.1 beta available on IBM Power Platform||Jan 23, 2015|
|Designing with Linux||Jan 22, 2015|
|Wondershaper—QOS in a Pinch||Jan 21, 2015|
- PostgreSQL, the NoSQL Database
- Sharing Admin Privileges for Many Hosts Securely
- HPC Cluster Grant Accepting Applications!
- Designing with Linux
- Linux-Based X Terminals with XDMCP
- Video Art: Experimental Animation and Video Techniques in Linux
- HTML5 for Audio Applications
- Rock Out with Your Console Out
- Wondershaper—QOS in a Pinch
- Kdenlive 0.8 Released
Editorial Advisory Panel
Thank you to our 2014 Editorial Advisors!
- Jeff Parent
- Brad Baillio
- Nick Baronian
- Steve Case
- Chadalavada Kalyana
- Caleb Cullen
- Keir Davis
- Michael Eager
- Nick Faltys
- Dennis Frey
- Philip Jacob
- Jay Kruizenga
- Steve Marquez
- Dave McAllister
- Craig Oda
- Mike Roberts
- Chris Stark
- Patrick Swartz
- David Lynch
- Alicia Gibb
- Thomas Quinlan
- Carson McDonald
- Kristen Shoemaker
- Charnell Luchich
- James Walker
- Victor Gregorio
- Hari Boukis
- Brian Conner
- David Lane