Which one is better - Glasses or Contact Lenses?

Ah, the great battle between glasses and contact lenses.  There are fierce supporters on both sides of this war, with each having their pros and cons.  Let’s look at the arguments behind each, and you can decide which you want to wear.

While it’s much easier to find advantages of contact lenses over glasses, let’s first look at why people prefer glasses.  First of all, some people prefer the look of glasses.  It gives people a studious, intelligent appearance.  Glasses can be fashionable, with many different styles.  Glasses can be easily removed.  If you want to lie down, you can just take them off.  This is not possible with contact lenses.   Finally, glasses are very affordable.  They can be reasonably priced and are significantly cheaper than contact lenses in the long run.

Contact lenses continue to increase in popularity.  They’re worn right on the eye, so your vision is more natural.  Peripheral vision is not an issue with contacts.  You have a complete field of view.  Contacts don’t have weight and a frame slowing sliding down your nose.  Contacts don’t fog up with changes in temperature.  Athletes prefer contacts because they don’t have to worry about glasses falling off or getting in the way.

If you’re undecided on which option will be best for you, try both of them.  Talk with your eye care doctor on which option will suit you better.  If you like glasses and contact lenses, many people wear a combination of the two.  Experiment with glasses and contact lenses and choose whichever makes you happier!

How to set up cron job in linux

What is a cron job?

As a network admin, its very important that we know the use of the crontab command which is used to setup cron jobs.

Cron job are used to schedule commands to be executed periodically. You can setup commands or scripts, which will repeatedly run at a set time. Cron is one of the most useful tool in Linux or UNIX like operating systems. The cron service (daemon) runs in the background and constantly checks the /etc/crontab file, /etc/cron.*/ directories. It also checks the /var/spool/cron/ directory

crontab is the command used to install, deinstall or list the tables (cron configuration file) used to drive the cron daemon in Vixie Cron. Each user can have their own crontab file, and though these are files in /var/spool/cron/crontabs, they are not intended to be edited directly. You need to use crontab command for editing or setting up your own cron jobs.

To edit your crontab file, type the following command at the UNIX / Linux shell prompt:$ crontab -e

Syntax of crontab (Field Description)

Your cron job looks as follows for user jobs:

 
1 2 3 4 5 /filepath ag1 ag2
 

OR

 
1 2 3 4 5 /root/runscript.tcl
 

Where,

• 1: Minute (0-59)
• 2: Hours (0-23)
• 3: Day (0-31)
• 4: Month (0-12 [12 == December])
• 5: Day of the week(0-7 [7 or 0 == sunday])
• /filepath - Absolute path of the script or command name to schedule* * * * * command to be executed

Note: Only use absolute paths in the cron. Do not use relative paths.

EXAMPLE CRON FILE

       # use /bin/sh to run commands, no matter what /etc/passwd says
       SHELL=/bin/sh
       # mail any output to 'paul', no matter whose crontab this is
       MAILTO=paul
       #
       # run five minutes after midnight, every day
       5 0 * * *       $HOME/bin/daily.job >> $HOME/tmp/out 2>&1

       # run at 2:15pm on the first of every month -- output mailed to paul
       15 14 1 * *     $HOME/bin/monthly

       # run at 10 pm on weekdays, annoy Joe
       0 22 * * 1-5    mail -s "It's 10pm" joe%Joe,%%Where are your kids?%

       23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday"

       5 4 * * sun     echo "run at 5 after 4 every sunday"