eshabe's blog

Program Pendukung

2011-03-16T21:12:00.000-07:00

Pada dasarnya, untuk mengikuti "Belajar Bahasa C" boleh menggunakan program seperti Visual C, Borland C atau yang lain. Namun agar lebih mudah memahami tulisan ini sebaiknya menggunakan program pendukung berupa compiler: GNU Compiler Collection atau gcc. Untuk mengetik program, bisa menggunakan gedit (Linux) atau Notepad++ (Windows) atau penyunting teks lain yang selama ini telah biasa digunakan. Sebagai gambaran, penulis menggunakan Ubuntu Linux 10.04 dg gcc versi 4.4.3 dan gedit.

Lihat! Program-program pendukung yang disarankan adalah program gratis bahkan bebas (free software)!

Mengapa Bahasa C?

2011-03-16T20:03:00.000-07:00

Pertanyaan semacam itu selalu muncul saat kita menawarkan sesuatu. Bahasa C adalah bahasa pemrogaman yang artinya ia hanyalah sebuah alat bantu atau bahan mentah. Alasan pemilihan alat atau bahan tentu saja tergantung kepada: hasil yang akan dicapai, kemudahan pembuatan dan ketersediaan.

Hasil Yang Akan Dicapai
Jika akan membuat web maka bahasa yang utama adalah HTML. Bahasa C bisa digunakan sebagai generator HTML. C menjadi salah satu pilihan saat akan membuat software sistem, atau aplikasi. Penggunaan C tidak terbatas pada aplikasi desktop, aplikasi level kontroler atau prosesor pun bisa dibuat menggunakan bahasa ini.

Kemudahan Pembuatan
Ketika hasil yang akan dicapai sudah ditentukan, misalnya aplikasi desktop POS untuk lingkungan sistem operasi Linux, maka bahasa-bahasa seperti perl, assembly, PHP tidak mudah untuk digunakan. Sedangkan C masih menjadi salah satu pilihan.

Ketersediaan
C telah tersedia untuk berbagai platform komputer dan sistem operasi. Pengguna Windows, Linux, MacOS X dan lain-lain bisa dengan mudah mendapatkan alat bantu pemrograman dengan C baik itu yang berbayar maupun yang gratis, baik itu yang berlisensi tertutup maupun yang bebas, baik itu yang visual maupun yang ketik manual.

What I like and dislike from Lucid Lynx (Ubuntu 10.4)

2010-05-06T09:32:00.000-07:00

I like...

Faster on boot and shutdown
More simple GUI than before
Latest Firefox version
Indicator Applet Session's status is work for both Empathy and Pidgin
Left side close window button
All of my laptop hardware is just work out of box

I dislike....

No GIMP, need to be installed
OpenVPN network-manager-plugin is not work well yet
Lesser games
Gwibber

dia : A program for drawing structured diagrams

2009-09-26T10:38:00.000-07:00

Word processor and spreadsheet applications can be used to draw a diagram; flow-chart or whatever diagrams. But we will find dificulties when doing in it because the applications are not designed for this job.

Ubuntu, the most growing GNU/Linux distribution, provide an application named Editor Diagram (dia) as dia-gnome package. The -gnome sufix show this application is developed by GNOME team and to do in GNOME desktop environment.

Just install dia use apt-get command line or Synaptic, or "Add/Remove..."

After installation completed, the application can be found in Applications -> Graphics -> Editor Diagram Dia.

There are more than 30 diagrams every simbols are provided already; flow-chart, jigsaw, logic, ladder, electrics, electronics, Gane and Sarson (DFD) and so on.

dia's working file is saved with .dia suffix and it can be exported to many file formats; DXF, PNG, JPG dan SVG and so on.

Screenshoot

Using Ubuntu Jaunty Jackalope - language-pack-id

Problem after update Ubuntu 8.04 Server software

2009-05-06T09:24:00.001-07:00

I just update Ubuntu 8.04 Server software by command:

$ sudo apt-get update && sudo apt-get upgrade

The process it self is ok, but my apache web server can not run.

$ sudo /etc/init.d/apache2 restart

Say error in /etc/apache2/sites-enabled/000-default.save

I remove the file then apache work fine again :)

Root without password in Ubuntu

2009-05-06T07:05:00.001-07:00

Since I use Hardy Heron, I found that we can get root console / command
prompt without a password.

I do not know, why Ubuntu team do this. But it was help me when I must
enter the admin functions but I do not know the admin user name and
password.

How to get in it?

When system is booting and prompt a GRUB menu, I press ESC key. Then I
select "Recovery mode". After the system show a selection action box, I
select "root". Than I get a sign: #

Deleting Old Files In Linux

2009-02-08T07:56:00.001-08:00

When my scheduled database backup run, I have many old files we do not neet them anymore. So, I have a question for my self: How to remove them automatically just after backup is done?

So, I try to read 'find' command manual. The command is "man find" (without double quotes) if you do not know :) then I found these option:

-atime n
File was last accessed n*24 hours ago. When find figures out
how many 24-hour periods ago the file was last accessed, any
fractional part is ignored, so to match -atime +1, a file has to
have been accessed at least two days ago.

-ctime n
File’s status was last changed n*24 hours ago. See the comments
for -atime to understand how rounding affects the interpretation
of file status change times.

-name pattern
Base of file name (the path with the leading directories
removed) matches shell pattern pattern. The metacharacters
(‘*’, ‘?’, and ‘[]’) match a ‘.’ at the start of the base name
(this is a change in findutils-4.2.2; see section STANDARDS CON‐
FORMANCE below). To ignore a directory and the files under it,
use -prune; see an example in the description of -path. Braces
are not recognised as being special, despite the fact that some
shells including Bash imbue braces with a special meaning in
shell patterns. The filename matching is performed with the use
of the fnmatch(3) library function. Don’t forget to enclose
the pattern in quotes in order to protect it from expansion by
the shell.

-delete
Delete files; true if removal succeeded. If the removal failed,
an error message is issued. If -delete fails, find’s exit sta‐
tus will be nonzero (when it eventually exits). Use of -delete
automatically turns on the -depth option.

So, with options combination I get a command:
$ find . -name 'backup_*.db' -ctime +30 -delete

That is! I put the command in my backup script than run by cron every weeks and my old files will be deleted just after backup is done.

2008-10-17T09:34:00.000-07:00

To get my work on time schedule, I must bring it as my homework. It is software development. For this purpose, I have to connect my office computer to home computer with VPN.

1st - ISP's Modem

Open firewall or port triggering: 1194 UDP
ThenVirtual Server, forward incoming connection 1194 port to my office computer's IP address.

2dn - Install OpenVPN

Office / Server: Ubuntu 8.04 (Hardy Heron) Server
Home / Client: Ubuntu 8.04 Desktop

Install openvpn in both computers:

sudo apt-get install openvpn

3rd - Configure the server: (see HOWTO for more)

cd /etc/openvpncp -r /usr/share/doc/openvpn/examples/easy-rsa/2.0/ ./easy-rsa/cd easy-rsa

(optionals)

nano ./vars

Change the values:

export KEY_COUNTRY=ID
export KEY_PROVINCE=KEPRIexport KEY_CITY=BATAMexport KEY_ORG="OpenVPN-TEST"
export KEY_EMAIL="eshabe@gimail.com"

(then):

source ./vars

./clean-all

./build-ca

Pay attention in “Common Name”. Example answer: "myfirstvpn"

./build-key-server server

Pay attention in...
“Common Name” - my answer is “server”
“Sign the certificate? [y/n]” - answer “y”
“1 out of 1 certificate requests certified, commit? [y/n]” - answer “y”

./build-key client1

./build-key client2

./build-key client3

./build-dh

Copy key files:

cd /etc/openvpn

cp easy-rsa/keys/server.crt .

cp easy-rsa/keys/server.key .

cp easy-rsa/keys/ca.crt .

cp easy-rsa/keys/dh1024.pem .

Copy example config file:

gunzip /usr/share/doc/openvpn/examples/sample-config-files/server.conf.gz

4th - Configure the client

Copy key files:

cd /etc/openvpn

scp eshabe@125.x.x.x:/etc/openvpn/easy-rsa/keys/client1.crt client.crt

scp eshabe@125.x.x.x:/etc/openvpn/easy-rsa/keys/client1.key client.key

scp eshabe@125.x.x.x:/etc/openvpn/easy-rsa/keys/ca.crt ca.crt

Copy example config file:

cp /usr/share/doc/openvpn/examples/sample-config-files/client.conf .

Edit config file:

nano client.conf

Change remote value:

remote 125.1.2.3 1194

5th - Try and activate
Try:
(server)

openvpn server.conf

(client)

openvpn client.conf

Yes!! openvpn is ready….

/etc/init.d/openvpn start

HowTo: No waiting time in Ubuntu's GRUB

2008-10-05T09:29:00.000-07:00

By default, Ubuntu display a GRUB menu and give us ten (10) seconds waiting time for user interaction. If you feel this waiting time is disturbing, you can remove the waiting time by edit the GRUB menu. Set 'timeout' value to 0 (zero).

From Terminal, type:

sudo nano /boot/grub/menu.lst

Change timeout value.

And, do not forget to activate hiddenmenu option. Why? By activating the option, although the timeout is 0 second, we can enter to the GRUB menu by pressing ESC key.

Save the file!

Create 'tar' file from a list

2008-10-05T08:38:00.001-07:00

Creating a 'tar' file is simple, but creating a 'tar' file from some files have different paths/directories is another case.

Example, when I want to create a tar file from path /home/eshabe/mydocs, I can use command: tar cvf mydoc.tar /home/eshabe/mydocs

But when I want to create a tar file from files:
/home/eshabe/mydocs/howto-create-tar-file-from-a-list
/etc/apache2/site-enables/000-default
/home/eshabe/mydocs/yes/i/am
/home/eshabe/.gnome2
...
?

I can create a tar file from command line: tar cvf mydoc.tar /home/eshabe/...

Another way is create a shell (sh) script to read a list file then create a tar file:

#!/bin/sh
# Create a 'tar' file from a list

n_program=`basename $0`
v_program=1.0.0d1
p_program=eshabe
t_program='2003.08.12'

RUNNAME='./shb-tarlist-run'

info_program ()
{
cat <<>
$n_program v$v_program
by: $p_program - $t_program
----------------------------------------------------------------------------
Function : create a tar file from a list file
Command : $nama_program LIST_FILE FILE.tar

LIST_FILE = a file contains list of files or directories
FILE.tar = result

pesan_program

}

if [ $# != 2 ]
then
info_program
exit
fi

printf "tar cvf $2 " > $RUNNAME
awk '{
printf "%s ", $0
}' $1 >> $RUNNAME

chmod a+x $RUNNAME
$RUNNAME
rm $RUNNAME

echo Done.