Unix and Linux Tips

Kamis, 18 November 2010

Unix Tip: CTRL-D ANOTHER USE

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3570 - November 18, 2010

http://www.ugu.com/sui/ugu/show?tip.today

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CTRL-D ANOTHER USE

Many Unix Admins use the C shell as their interactive shell.
An often used feature of Csh is file completion - initiated
with 'set filec'. It allows the Csh user to type in partial
file names, and then press escape to get them completed where
possible. A little known side effect of this is that
Control-D (^D) will now generate file listings in the middle of
command lines.

Example 1: (where @ is a space)
host > @^D
Lists the current directory

Example 2:
host >ln -s /usr/^D
Lists the /usr directory

host >tar cvf /dev/nrtape /usr/m^D
Lists all m* files in the /usr directory

In each case, after the listing, you get a new command line and are
placed at the last point of edit.

Very handy if you you know what you wanted to do but forgot what you
wanted to do it with!

This tip generously supported by: mikal.dunn@halliburton.com

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Rabu, 17 November 2010

Unix Tip: HIDE THOSE FILES

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3569 - November 17, 2010

http://www.ugu.com/sui/ugu/show?tip.today

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HIDE THOSE FILES

If you want to have some hidden directories on your server (warez etc.)
then make a directory with permission 111.

% chmod 111 foo/

All the contents will become hidden:

% cd foo
% ls -al
Cannot access directory .: Permission denied

The directory will have to opened back up (755) in order to see or access
the files or the directory. To remove the directory and its contents, it
will also need to have the permissions opened.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Selasa, 16 November 2010

Unix Tip: TCSH AND RMSTAR

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3568 - November 16, 2010

http://www.ugu.com/sui/ugu/show?tip.today

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TCSH AND RMSTAR

tcsh has a nice built in variable:
set rmstar

Whenever you type the command:

% rm *

The shell will ask you to confirm, this prevents you from deleting
all your files accidentally.

Add "set rmstar" in you .cshrc file for your own benefit.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Senin, 15 November 2010

Unix Tip: PERFORMANCE OF CROND TASKS

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3567 - November 15, 2010

http://www.ugu.com/sui/ugu/show?tip.today

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PERFORMANCE OF CROND TASKS

A good tip for getting better performance in crond tasks
is choosing a better time for launching them.

If the process that we want to launch needs few time,
but can overload the system easily, you can launch
the task in hours that the work is busy and -and HERE
is the tip- in strange minutes. That's why lots of
people launch their crons at midnight, but
nobody uses to do it at 00:13, in example.

That tip can obtain his best in hourly-launched
tasks. If that kind of tasks are launched all at
the same time, the system will overload without
any use. You can delay that kind of tasks (one
at 13th minute, other at 17th minute,other at
27th minute...) and obtain better performance
without work. That will avoid overloading caused
by launching several tasks at the same time.

The best is that administration tasks do
not overlap, but this is not always possible.
If you can do it, it's better you do it.

Using nice is also a good idea.

But the best is making a log of the uptime during
a week. You can be surprise, because all the staff
of a department of a firm use to do the coffee-break
at the same time; it's the perfect time for making
some administrative tasks. :-)
But do not clear the forbidden extensions -the famous
find /home -name core -exec \{\} \; and other stuff
like tmps, ~s and so on- of the system
at work time, or you will have a queue of staff people
very, very angry knocking at your door.

This tip generously supported by: irbis@activanet.es

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Minggu, 14 November 2010

Unix Tip: SHELL SCRIPTING A SQLPLUS SCRIPT

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3566 - November 14, 2010

http://www.ugu.com/sui/ugu/show?tip.today

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SHELL SCRIPTING A SQLPLUS SCRIPT

Here is a tip on how to run sqlplus scripts within a shell script.
It is an example of how to pass database values into shell variables
and to make shell scripts more dynamic. This maybe elementary to some
folks but hope it helps others.....Here is the syntax:

#!/bin/sh
dummyvar=`sqlplus -s username/password <<end
set pagesize 0 feedback off ver off heading off echo off
select sysdate from dual;
exit;
end`
echo "system date is " $dummyvar