How to ping a web site periodically
Answer:
1. Setup a cron job
crontab -e
2. Enter the job detail as following
1 * * * * /usr/bin/wget -O - -q -t 1 http://www.example.com/cron.php
3. Fine tune the crontab configurations if needed.
Jan 022010
Linux Ask!
Jan 022010
How to perform syntax check for Perl program
Answer:
Assume you have a Perl script test.pl, try run the command
perl -c test.pl
Syntax error will be displayed without running the code actually.
Jan 022010
How to alter the priority of running processes
Answer:
The basic syntax is as the following
renice {priority} pid
Where priority range from -20 to 19 (lowest priority)
For example, to set the priority of pid 755 to -19, try
sudo renice 19 755
If you want to set by process name instead of pid, you can use
sudo renice 19 `pgrep apache2`
Where apache2 is the process name you want to set.
Jan 022010
How to sort a hash in Perl
Answer:
# %hash is the hash to sort
@keys = sort { criterion() } (keys %hash);
foreach $key (@keys) {
$value = $hash{$key};
# do something with $key, $value
}
Jan 022010
How to return the directory portion of a pathname
Answer:
Use the "dirname" command, e.g.
# dirname /usr/sbin/ufw
/usr/sbin
