Howto setup mysql-cluster (beginners tutorial)
Introduction
This HOWTO is designed for a classic setup of two servers behind a load-balancer. The aim is to have true redundancy – either server can be unplugged and yet the site will remain up.
Notes:
You MUST have a third server as a management node but this can be shut down after the cluster starts. Also note that I do not recommend shutting down the management server (see the extra notes at the bottom of this document for more information). You can not run a MySQL Cluster with just two servers And have true redundancy.
Although it is possible to set the cluster up on two physical servers you WILL NOT GET the ability to “kill” one server and for the cluster to continue as normal. For this you need a third server running the management node.
we are going to talk about three servers:
node01.example.com 192.168.0.10
node02.example.com 192.168.0.20
node03.example.com 192.168.0.30
Servers node01 and node02 will be the two that end up “clustered”. This would be perfect for two servers behind a loadbalancer or using round robin DNS and is a good replacement for replication. Server node03 needs to have only minor changes made to it and does NOT require a MySQL install. It can be a low-end machine and can be carrying out other tasks.
Get the software:
For Generally Available (GA), supported versions of the software, download from
http://www.mysql.com/downloads/cluster/
Make sure that you select the correct platform – in this case, “Linux – Generic” and then the correct architecture (for LINUX this means x86 32 or 64 bit).
Note: Only use MySQL Server executables (mysqlds) that come with the MySQL Cluster installation.
STAGE1: Installation of Data and SQL nodes on node01 and node02
On each of the machines designated to host data or SQL nodes(in our case node01 and node02), perform the following steps as the system root user:
- create a new mysql user group, and then add a mysql user to this group:
shell> groupadd mysql shell> useradd -g mysql mysql
- Change location to the directory containing the downloaded file, unpack the archive, and create a symlink to the mysql directory named mysql. Note that the actual file and directory names vary according to the MySQL Cluster version number.
shell> cd /var/tmp shell> tar -C /usr/local -xzvf mysql-cluster-gpl-7.1.5-linux-x86_64-glibc23.tar.gz
shell> ln -s /usr/local/mysql-cluster-gpl-7.1.5-linux-i686-glibc23 /usr/local/mysql
shell> export PATH=$PATH:/usr/local/mysql/bin
shell> echo “export PATH=\$PATH:/usr/local/mysql/bin” >> /etc/bash.bashrc
- Change location to the mysql directory and run the supplied script for creating the system databases:
shell> cd mysql shell> ./scripts/mysql_install_db –user=mysql
- Set the necessary permissions for the MySQL server and data directories:
shell> chown -R root . shell> chown -R mysql data
shell> chgrp -R mysql .
- Copy the MySQL startup script to the appropriate directory, make it executable, and set it to start when the operating system is booted up:
shell> cp support-files/mysql.server /etc/init.d/mysql shell> chmod +x /etc/init.d/mysql
shell> update-rc.d mysql defaults
STAGE2: Installation of Management node on node03
Installation of the management node does not require the mysqld binary. Only the MySQL Cluster management server (ndb_mgmd) is required; I assume that you have placed mysql-cluster-gpl-7.1.5-linux-i686-glibc23.tar.gz in /var/tmp.
As system root perform the following steps to install ndb_mgmd and ndb_mgm on the Cluster management node host (node02):
- Change location to the /var/tmp directory, and extract the ndb_mgm and ndb_mgmd from the archive into a suitable directory such as /usr/local/bin:
shell> cd /var/tmp shell> tar -zxvf mysql-cluster-gpl-7.1.5-linux-i686-glibc23.tar.gz
shell> cd /usr/local/mysql-cluster-gpl-7.1.5-linux-i686-glibc23
shell> cp bin/ndb_mgm* /usr/local/bin
- Change location to the directory into which you copied the files, and then make both of them executable:
shell> cd /usr/local/bin shell> chmod +x ndb_mgm*
STAGE3: Configuration of Management node
The first step in configuring the management node is to create the directory in which the configuration file can be found and then to create the file itself. For example (running as root):
| shell> mkdir /var/lib/mysql-cluster
shell> cd /var/lib/mysql-cluster shell> vi config.ini |
For our setup, the config.ini file should read as follows:
| [ndbd default]
NoOfReplicas=2 DataMemory=80M IndexMemory=18M [tcp default] [ndb_mgmd] hostname=192.168.0.30 # Hostname or IP address of MGM node datadir=/var/lib/mysql-cluster # Directory for MGM node log files [ndbd] hostname=192.168.0.10 # Hostname or IP address datadir=/usr/local/mysql/data # Directory for this data node’s data files [ndbd] hostname=192.168.0.20 # Hostname or IP address datadir=/usr/local/mysql/data # Directory for this data node’s data files [mysqld] hostname=192.168.0.10 # Hostname or IP address [mysqld] hostname=192.168.0.20 # Hostname or IP address |
STAGE4: Configuration of Data and SQL nodes
The first step in configuring the management node is to create the directory in which the configuration file can be found and then to create the file itself. For example (running as root):
| shell> vi /etc/my.cnf |
Note :
We show vi being used here to create the file, but any text editor should work just as well.
For each data node and SQL node in our setup, my.cnf should look like this:
| [client]
port = 3306 socket = /tmp/mysql.sock [mysqld] port = 3306 socket = /tmp/mysql.sock skip-locking ndbcluster # run NDB storage engine ndb-connectstring=192.168.0.30 # location of management server [mysql_cluster] ndb-connectstring=192.168.0.30 # location of management server |
Important :
Once you have started a mysqld process with the NDBCLUSTER and ndb-connectstring parameters in the [mysqld] in the my.cnf file as shown previously, you cannot execute any CREATE TABLE or ALTER TABLE statements without having actually started the cluster. Otherwise, these statements will fail with an error.
STAGE4: Starting the MySQL Cluster
Starting the cluster is not very difficult after it has been configured. Each cluster node process must be started separately, and on the host where it resides. The management node should be started first, followed by the data nodes, and then finally by any SQL nodes:
- On the management host(node03), issue the following command from the system shell to start the management node process:
shell> ndb_mgmd -f /var/lib/mysql-cluster/config.ini –configdir=/var/lib/mysql-clusetr - On each of the Data/SQL node hosts, run these commands to start the ndbd and mysql server process:
shell> /usr/local/mysql/bin/ndbd shell> /etc/init.d/mysql start
If all has gone well, and the cluster has been set up correctly, the cluster should now be operational. You can test this by invoking the ndb_mgm management node client. The output should look like that shown here:
| node03:~# ndb_mgm
– NDB Cluster — Management Client – ndb_mgm> SHOW Connected to Management Server at: localhost:1186 Cluster Configuration ——————— [ndbd(NDB)] 2 node(s) id=2 @192.168.0.10 (mysql-5.1.44 ndb-7.1.5, Nodegroup: 0, Master) id=3 @192.168.0.20 (mysql-5.1.44 ndb-7.1.5, Nodegroup: 0) [ndb_mgmd(MGM)] 1 node(s) id=1 @192.168.0.30 (mysql-5.1.44 ndb-7.1.5) [mysqld(API)] 2 node(s) id=4 @192.168.0.10 (mysql-5.1.44 ndb-7.1.5) id=5 @192.168.0.20 (mysql-5.1.44 ndb-7.1.5) |
STAGE5: Testing the Setup
If you are OK to here it is time to test mysql. On either server node01 or node02 enter the following commands: Note that we have no root password yet:
| shell> mysql
create database testdb; use test; CREATE TABLE cluster_test (i INT) ENGINE=NDBCLUSTER; INSERT INTO cluster_test (i) VALUES (1); SELECT * FROM cluster_test; |
You should see 1 row returned (with the value 1).
If this works, now go to the other server and run the same SELECT and see what you get. Insert from that host and go back to previous host and see if it works. If it works then congratulations!
Save 90% on international calls and sms with Vopium
If you are living abroad or frequently call your family and friends abroad you can save upto 90% on international calls and sms with Vopium, a Copenhagen – Denmark based company. 
Vopium provides it’s users variety of simple ways to make international calls and sms via it’s web portal and mobile application, Vopium is a mobile phone application supported on variety of platforms (symbian, iphone, android, java).
Apart from international calls and sms plans, Vopium enables it’s users to talk and chat using Skype, Google Talk, Msn and Yahoo.
Currently Vopium is available in 18 countries including Australia, Belgium, Denmark, France, Finland, Germany, Netherlands, Italy, Norway, Spain, Switzerland, Sweden, UK & USA.
To find out more and get started with Vopium, visit vopium.com
retrieve skype contact photos using python
tonight i was looking for a way to retrieve display pictures of my skype contacts from .dbb files and ended up with this small piece of code. i don’t find it much useful though but someone might be interesting so here it is.
#!/usr/bin/env python
#
# Author Ghulam Mustafa <mustafa.pk@gmail.com>
#
## This program is free software; you can redistribute it and/or
## modify it under the terms of the GNU General Public License version
## 2 as published by the Free Software Foundation.
## This program is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
## General Public License version 2 for more details.
## You should have received a copy of the GNU General Public License
## version 2 along with this program; if not, write to the Free
## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
## MA 02110-1301, USA.
profile = '/home/mustafa/.Skype/cyrenity/'
skypefiles = ["user256", "user1024", "user4096", "user16384", "user32768", "user65536",
"profile256", "profile1024", "profile4096", "profile16384", "profile32768"]
##retrieve contents of skype binary files and store them in a single variable
skbin = []
n = 0
for f in skypefiles:
fil = "%s%s.dbb" % (profile, f)
try: skbin.append(file(fil, "rb").read())
except: pass
n = n + 1
binary = "".join(skbin)
##
## get_icon(username, binary)
## returns
## True if successfull
## None if failed
## -1 if user not found
def get_icon(buddy, binary):
startmark = "\xff\xd8"
endmark = "\xff\xd9"
startfix = 0
endfix = 2
nick_start = "\x03\x10%s" % buddy
nick_end = "0"
nickstart = binary.find(nick_start)
if nickstart == -1: return -1
nickend = binary.find(nick_end, nickstart)
handle = binary[nickstart+2:nickend]
blockstart = binary.rfind("l33l", 0, nickend)
imgstart = binary.find(startmark, blockstart, nickend)
imgend = binary.find(endmark, imgstart)
imgstart += startfix
imgend += endfix
if (imgstart < 1): return None
##print "JPG %s from %d to %d" % (handle, imgstart, imgend)
jpg = binary[imgstart:imgend]
jpgfile = file("%s.jpg" % (handle), "wb")
jpgfile.write(jpg)
jpgfile.close()
return True
users = ['cyrenity', 'gmustafa9']
for user in users:
status = get_icon(user, binary)
if status and status != -1:
print "success [%s]" % user
else:
print "failed[%s] [%s]" % (status, user)
p.s. you are encouraged to send me update if you found a bug or fix something.
howto install Karaka: xmpp gateway to skype!
You came here searching for howto install karaka. Vipdia Limited doesn’t tell much on how to setup karaka step by step, yesterday someone asked this question on karaka-discuss mailing list, this post is helpful for you if you are thinking about giving karaka a try.
more here: http://groups.google.com/group/karaka-discuss/browse_thread/thread/d6eb8fcd61bd3e05
update and retrieve twitter timeline from linux shell
you can update your twitter status and follow feeds using linux shell, this is a quick tip for linux lover’s, this is the reason i prefer linux over other operating systems is it’s total usefullnes,
to post your status on twitter type:
curl -s -u username:password -d status="your_status_message goes here" http://twitter.com/statuses/update.xml > /dev/null
replace username, password and message to post with the your own.
to follow feeds from twitter.
curl -s -u username:password http://twitter.com/statuses/friends_timeline.rss | grep title | sed -e 's/]*>//g'
replace username and password with your own. above command will retrieve recent rss entries from your twitter timeline.
one more cool thing you can do with this long command is to enclose it put it in a text file, let’s say “/usr/local/bin/get-twits” and make it exectuable by issuing
chmod a+x /usr/local/bin/get-twits
now open a new terminal windows and type: watch --interval=60 get-twits
this command will keep your terminal windows updated with recent twitter updates.
enjoy
cloning harddrives over network
To clone identical drives in a linux system you can use dd command, dd command makes it really easy.
dd if=/dev/hda of=/dev/hdb
above command will clone hda to hdb (partitions, boot record etc), but what if you have to clone a drive that is not attached to same system?
I found a really interesting way to transfer files over the network simple by using netcat and dd.
- Boot the machine (where second drive is attached) with a live cd distro like Ubuntu or Knoppix. Setup networking or let the DHCP server assign an ip automatically. My DHCP assigned this machine ip 192.168.0.21
- run following command on this machine
nc -l -p 7777 | dd of=/dev/hdb(where /dev/hdb is the target drive)
- Now come to the machine where you have attached the drive to be cloned and issue following command.
dd if=/dev/hda | nc 192.168.0.21 7777(/dev/hda is the drive to be cloned)
It will take time (usually several hours) depending on size of the drive. If you are worried about bandwidth you can pipe through gzip to compress and uncompress the streamed data on source and destination machine respectively, to do this you would run following commands.
On target machine:
nc -l -p 7777 | gzip –dfc | dd of=/dev/hdb
And on source machine.
dd if=/dev/hda | gzip –cf | nc 192.168.0.21 7777
have fun with dd and nc
asterisk 1.2 with realtime ldap driver
I have created an auto install script based on http://www.cahilig.org/install-asterisk-12-auto-install-script-centos-4-and-centos-5 to install Asterisk 1.2 with ldap realtime driver support (modified original script to enable realtime ldap support).
This script should work almost with any(Redhat, Centos, Mandrake, Debian, Slackware) Linux distro
Before running this script you must install following packages.
For Centos, Redhat:
yum install openldap-devel gcc kernel-devel bison openssl-devel libtermcap-devel ncurses-devel
For Debian, Ubuntu:
apt-get install libldap2-dev build-essential linux-headers-`uname -r` libncurses5-dev libssl-dev
You can download the script from here, simply run the script to start installation process.
download Asterisk schema for OpenLdap here
Installer and installation process is not tested, if you find any problem please let me know.
#!/bin/sh #Asterisk Download page ZAPTEL="http://downloads.digium.com/pub/zaptel/releases/zaptel-1.2.9.tar.gz" ASTERISK="http://downloads.digium.com/pub/asterisk/releases/asterisk-1.2.30.tar.gz" ASTERISKADDONS="http://downloads.digium.com/pub/asterisk/releases/asterisk-addons-1.2.9.tar.gz" RTLDAP="http://free.oxymium.net/Asterisk/res_config_ldap.tgz" RTLDAPPATCH="http://mustafa.pk.googlepages.com/res_config_ldap.c.patch" CONFIGPATCH="http://mustafa.pk.googlepages.com/config.c.patch" MAKEFILEPATCH="http://mustafa.pk.googlepages.com/resmkfile.patch" #Asterisk Package ZAPPACKAGE="zaptel-1.2.9.tar.gz" ASTPACKAGE="asterisk-1.2.30.tar.gz" ASTADDONSPACKAGE="asterisk-addons-1.2.9.tar.gz" #Asterisk Folder ZAPFOLDER="zaptel-1.2.9" ASTFOLDER="asterisk-1.2.30" ASTADDONSFOLDER="asterisk-addons-1.2.9" REALTIMEDIRVER="res_config_ldap.tgz" if [ -f /etc/redhat-release ] ; then DISTRO="redhat" elif [ -f /etc/debian_version ] ; then DISTRO="debian" elif [ -f /etc/SUSE-release ] ; then DISTRO="redhat" elif [ -f /etc/mandrake-release ] ; then DISTRO="mandrake" elif [ -f /etc/slackware-release ] ; then DISTRO="slackware" elif [ -f /etc/gentoo-release ] ; then DISTRO="gentoo" fi echo "Downloading and extracting zaptel and asterisk source" cd /usr/local/src/ if [ ! -e $ZAPPACKAGE ]; then wget $ZAPTEL fi if [ ! -e $ASTPACKAGE ]; then wget $ASTERISK fi if [ ! -e $ASTADDONSPACKAGE ]; then wget $ASTERISKADDONS fi tar -zvxf $ZAPPACKAGE tar -zvxf $ASTPACKAGE tar -zvxf $ASTADDONSPACKAGE echo "Installing zaptel" cd $ZAPFOLDER make clean make make install cd .. echo "Installing asterisk" cd $ASTFOLDER echo "Downloading patches" wget $CONFIGPATCH wget $MAKEFILEPATCH patch -p0<resmkfile.patch patch -p0<config.c.patch echo "Downloading Realtime Ldap driver" cd res wget $RTLDAP tar -zxvf $REALTIMEDIRVER wget $RTLDAPPATCH patch -p0<res_config_ldap.c.patch cd ../configs wget http://mustafa.pk.googlepages.com/extconfig.conf.sample wget http://mustafa.pk.googlepages.com/res_ldap.conf.sample cd .. make clean make make install make samples cp contrib/init.d/rc.$DISTRO.asterisk /etc/init.d/asterisk cd .. echo "Installing asterisk-addons" cd $ASTADDONSFOLDER make clean make make install echo "Loading ztdummy driver" modprobe zaptel modprobe ztdummy echo "adding rules to /etc/rc.local" echo "modprobe zaptel modprobe ztdummy " >> /etc/rc.local echo "Downloading open source g729 codec" cd /usr/lib/asterisk/modules/ wget http://asterisk.hosting.lv/bin12/codec_g729-ast12-gcc4-glibc-pentium4.so echo "Running Asterisk" /etc/init.d/asterisk start echo "***********************************************************************" echo "* INSTALLATION SUCCESSFUL *" echo "***********************************************************************" echo "* You can test if Asterisk installed successfully using *" echo "* asterisk -ncrvvv and start configuring your dial plan *" echo "***********************************************************************" exit
“kill -9″ song by monzy
really funny rap song about “kill -9″ command by Monzy at stanford university.
evolution of a programmer
High School/Junior High
10 PRINT "HELLO WORLD" 20 END
First year in College
program Hello(input, output)
begin
writeln('Hello World')
end.
Senior year in College
(defun hello
(print
(cons 'Hello (list 'World))))
New professional
#include
void main(void)
{
char *message[] = {"Hello ", "World"};
int i;
for(i = 0; i < 2; ++i)
printf("%s", message[i]);
printf("\n");
}
Seasoned professional
#include
#include
class string
{
private:
int size;
char *ptr;
public:
string() : size(0), ptr(new char('')) {}
string(const string &s) : size(s.size)
{
ptr = new char[size + 1];
strcpy(ptr, s.ptr);
}
~string()
{
delete [] ptr;
}
friend ostream &operator <<(ostream &, const string &);
string &operator=(const char *);
};
ostream &operator<<(ostream &stream, const string &s)
{
return(stream << s.ptr);
}
string &string::operator=(const char *chrs)
{
if (this != &chrs)
{
delete [] ptr;
size = strlen(chrs);
ptr = new char[size + 1];
strcpy(ptr, chrs);
}
return(*this);
}
int main()
{
string str;
str = "Hello World";
cout << str << endl;
return(0);
}
Master Programmer
[
uuid(2573F8F4-CFEE-101A-9A9F-00AA00342820)
]
library LHello
{
// bring in the master library
importlib("actimp.tlb");
importlib("actexp.tlb");
// bring in my interfaces
#include "pshlo.idl"
[
uuid(2573F8F5-CFEE-101A-9A9F-00AA00342820)
]
cotype THello
{
interface IHello;
interface IPersistFile;
};
};
[
exe,
uuid(2573F890-CFEE-101A-9A9F-00AA00342820)
]
module CHelloLib
{
// some code related header files
importheader();
importheader();
importheader();
importheader("pshlo.h");
importheader("shlo.hxx");
importheader("mycls.hxx");
// needed typelibs
importlib("actimp.tlb");
importlib("actexp.tlb");
importlib("thlo.tlb");
[
uuid(2573F891-CFEE-101A-9A9F-00AA00342820),
aggregatable
]
coclass CHello
{
cotype THello;
};
};
#include "ipfix.hxx"
extern HANDLE hEvent;
class CHello : public CHelloBase
{
public:
IPFIX(CLSID_CHello);
CHello(IUnknown *pUnk);
~CHello();
HRESULT __stdcall PrintSz(LPWSTR pwszString);
private:
static int cObjRef;
};
#include
#include
#include
#include
#include "thlo.h"
#include "pshlo.h"
#include "shlo.hxx"
#include "mycls.hxx"
int CHello::cObjRef = 0;
CHello::CHello(IUnknown *pUnk) : CHelloBase(pUnk)
{
cObjRef++;
return;
}
HRESULT __stdcall CHello::PrintSz(LPWSTR pwszString)
{
printf("%ws\n", pwszString);
return(ResultFromScode(S_OK));
}
CHello::~CHello(void)
{
// when the object count goes to zero, stop the server
cObjRef--;
if( cObjRef == 0 )
PulseEvent(hEvent);
return;
}
#include
#include
#include "pshlo.h"
#include "shlo.hxx"
#include "mycls.hxx"
HANDLE hEvent;
int _cdecl main(
int argc,
char * argv[]
) {
ULONG ulRef;
DWORD dwRegistration;
CHelloCF *pCF = new CHelloCF();
hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
// Initialize the OLE libraries
CoInitializeEx(NULL, COINIT_MULTITHREADED);
CoRegisterClassObject(CLSID_CHello, pCF, CLSCTX_LOCAL_SERVER,
REGCLS_MULTIPLEUSE, &dwRegistration);
// wait on an event to stop
WaitForSingleObject(hEvent, INFINITE);
// revoke and release the class object
CoRevokeClassObject(dwRegistration);
ulRef = pCF->Release();
// Tell OLE we are going away.
CoUninitialize();
return(0); }
extern CLSID CLSID_CHello;
extern UUID LIBID_CHelloLib;
CLSID CLSID_CHello = { /* 2573F891-CFEE-101A-9A9F-00AA00342820 */
0x2573F891,
0xCFEE,
0x101A,
{ 0x9A, 0x9F, 0x00, 0xAA, 0x00, 0x34, 0x28, 0x20 }
};
UUID LIBID_CHelloLib = { /* 2573F890-CFEE-101A-9A9F-00AA00342820 */
0x2573F890,
0xCFEE,
0x101A,
{ 0x9A, 0x9F, 0x00, 0xAA, 0x00, 0x34, 0x28, 0x20 }
};
#include
#include
#include
#include
#include
#include "pshlo.h"
#include "shlo.hxx"
#include "clsid.h"
int _cdecl main(
int argc,
char * argv[]
) {
HRESULT hRslt;
IHello *pHello;
ULONG ulCnt;
IMoniker * pmk;
WCHAR wcsT[_MAX_PATH];
WCHAR wcsPath[2 * _MAX_PATH];
// get object path
wcsPath[0] = '';
wcsT[0] = '';
if( argc > 1) {
mbstowcs(wcsPath, argv[1], strlen(argv[1]) + 1);
wcsupr(wcsPath);
}
else {
fprintf(stderr, "Object path must be specified\n");
return(1);
}
// get print string
if(argc > 2)
mbstowcs(wcsT, argv[2], strlen(argv[2]) + 1);
else
wcscpy(wcsT, L"Hello World");
printf("Linking to object %ws\n", wcsPath);
printf("Text String %ws\n", wcsT);
// Initialize the OLE libraries
hRslt = CoInitializeEx(NULL, COINIT_MULTITHREADED);
if(SUCCEEDED(hRslt)) {
hRslt = CreateFileMoniker(wcsPath, &pmk);
if(SUCCEEDED(hRslt))
hRslt = BindMoniker(pmk, 0, IID_IHello, (void **)&pHello);
if(SUCCEEDED(hRslt)) {
// print a string out
pHello->PrintSz(wcsT);
Sleep(2000);
ulCnt = pHello->Release();
}
else
printf("Failure to connect, status: %lx", hRslt);
// Tell OLE we are going away.
CoUninitialize();
}
return(0);
}
Apprentice Hacker
#!/usr/local/bin/perl
$msg="Hello, world.\n";
if ($#ARGV >= 0) {
while(defined($arg=shift(@ARGV))) {
$outfilename = $arg;
open(FILE, ">" . $outfilename) || die "Can't write $arg: $!\n";
print (FILE $msg);
close(FILE) || die "Can't close $arg: $!\n";
}
} else {
print ($msg);
}
1;
Experienced Hacker
#include
#define S "Hello, World\n"
main(){exit(printf(S) == strlen(S) ? 0 : 1);}
Seasoned Hacker
% cc -o a.out ~/src/misc/hw/hw.c % a.out
Guru Hacker
% cat Hello, world. ^D
New Manager
10 PRINT "HELLO WORLD" 20 END
Middle Manager
mail -s "Hello, world." bob@b12 Bob, could you please write me a program that prints "Hello, world."? I need it by tomorrow. ^D
Senior Manager
% zmail jim I need a "Hello, world." program by this afternoon.
Chief Executive
% letter letter: Command not found. % mail To: ^X ^F ^C % help mail help: Command not found. % damn! !: Event unrecognized % logout
