Transcript LIS651 lecture 1 PHP basics

LIS651 lecture 5
origins of wotan
direct use of wotan
Thomas Krichel
2008-11-23
Early Computing History
• In the 1940s and 1950s, all computers were
personal computers in the sense that a user
would sign up to use the machine and then take
over the whole machine for that period.
• The early 1960s were dominated by batch
systems in which a user would submit a job on
punched cards and wait, usually hours, before
any printed output appeared.
Early Computing History
• To get around this unproductive environment,
the concept of timesharing was invented by
Dartmouth College and M.I.T.
• The M.I.T system CTSS (Compatible Time
Sharing System) was an enormous success.
• M.I.T., Bell Labs, and General Electric created a
second generation timesharing system named
MULTICS (Multiplexed Information and
Computing Service).
Early UNIX History
• At Bell Labs, Ken Thompson decided to write a
stripped down version of MULTICS for the very
small PDP-7 minicomputer which he called
UNICS.
• Dennis Ritchie, also at Bell Labs, joined
Thompson in further developments of what was
now called UNIX.
• Together they ported the system the the larger
and very popular PDP-11/20 and PDP-11/45
minicomputers.
Early UNIX History
• In 1974, Ritchie and Thompson published a
paper about UNIX and received the prestigious
ACM Turing Award.
• This publication stimulated many universities to
request a copies of UNIX.
• Since Bell Labs, part of AT&T, was not allowed
to be in the computer business, it licensed UNIX
to universities.
• Result: UNIX was a hit on campus.
UNIX Structure
• The kernel is the core of the UNIX system,
controlling the system hardware and
performing various low-level functions.
The other parts of the UNIX system, as
well as user programs, call on the kernel
to perform services for them.
• The shell is the command interpreter for
the UNIX system. The shell accepts user
commands and is responsible for seeing
that they are carried out.
BSD UNIX
• One of the many universities that had
received license for UNIX was the
University of California at Berkeley.
• Aided by many government grants,
Berkeley released an improved version
named 1BSD (First Berkeley Software
Distribution)
• BSD added many new features including a
new visual editor (vi) and a new shell
(csh).
Two UNIX Versions
• Because of these and other
enhancements, many companies based
their UNIX on Berkeley’s version as
opposed to AT&T’s so-called System V.
• By the late 1980s, two different and
somewhat incompatible versions of UNIX
were in widespread use: 4.3 BSD and
System V release 3.
UNIX Standards
• In addition, every vendor added its own
nonstandard enhancements.
• In an attempt to unify the troops, the IEEE
Standards Board undertook the POSIX Project
(POS for Portable Operating System) and IX to
make it UNIX like.
• POSIX 1003.1 emerged as a common ground
standard.
• 1003.1 is the intersection of System V and BSD.
(a feature had to be on both to be included in the
standard)
GNU
• GNU is a project started by Richard M.
Stallman (RMS) to write a completely free
implementation of Unix available.
• GNU stands for “GNU is not Unix”
• Most of Unix has been rewritten by him and
his friends.
• Many other software packages have been
released for free. Stallman pioneered a
particular concept of free software.
free software according to RMS
• Free software comes with four freedoms
– The freedom to run the software, for any
purpose
– The freedom to study how the program works,
and adapt it to your needs
– The freedom to redistribute copies so you can
help your neighbor
– The freedom to improve the program, and
release your improvements to the public, so
that the whole community benefits
the GNU public license
• Richard M. Stallman created the GNU
public license.
• The license restricts the right of software
users to add restrictions on the use of
derivative products.
• The idea is that when you get free software,
you can not restrict the freedom of users of
derivative software.
UNIX-like Systems
• MINIX, by Andrew Tanenbaum, used a
microkernel design with only 1600 lines of
C and 800 lines of assembler in its first
version.
• In 1991, a Finnish student named Linus
Torvalds released another UNIX clone
named Linux. It is a UNIX kernel for Intel
processors.
• FreeBSD is a competitor to Linux, started
in 1993.
Linux
• Linux is a monolithic UNIX kernel.
• Linux quickly grew in size and functionality.
• Version 1, shipped in 1994, contained about
165,000 lines of code.
• Version 2 in 1996 contained about 470,00 lines
of C and 8000 lines of assembler.
• Linux is released under the GNU public license,
which, very basically means that anyone can
copy and change it.
Linux Distributions
• Linux itself is free. It is aggregated with
installation and management tools, and
many other software packages, and made
available for a small fee by various vendors
on CD.
• These aggregates are known as
distributions.
• The one used by wotan is called Debian. It
packages Linux with GNU software almost
excusively.
communication with wotan
• For file editing and manipulation, we use
putty.
• For file transfer, we use winscp.
• Both are available on the web.
• The protocol is ssh, the secure shell, based
public-key cryptography.
installing putty
• Go to your favorite search engine to search
for putty.
• If you have administrator rights install the
installer version.
• Since you have already installed winscp,
you should have no further problems.
putty options
• In the window/translation choose UTF-8,
always.
• Find out what the size of your screen is of
screen that your are using for the font that
you are using, and save that in your
session.
• For wotan, the port is 22, ssh.
• You can choose to disable the annoying
bell.
Diffie and Hellman (1978)
• Let P be the plaintext, C be the cyphertext. E() is
the encryption key and D() is the decryption key.
• Then we have public key cryptography if
– 1. D(E(P))=P
– 2. D() can not be broken by chosen plaintext attack.
– 3. Knowing E() will give you no clue about D().
• E() can then be made public and is referred to as
the public key, D() is the private key.
• It is possible to find key pairs that have these
properties.
Authentication
• I want to securely login to a host machine.
• I send the hast an encrypted message ``hey, I am
Thomas, my public key is 7ni820g=0...''
• Machine then knows how to send me messages
that other people can not decode.
• But it can not be sure that it was me who sent the
message. An intruder may have done that since
me public key is public.
• This problem is solved by challenge/response
challenge/response
• To find out if I am the person that I claim to
be, the machine encodes a random
number, and challenges me to decode that
number.
• If I can decode the challenge, I must be the
person whom I claim I am.
key creation
• “ssh-keygen” is the command to use to
create a key. Answer all questions with the
<ENTER> key.
• “cd .ssh” and “ls -l” shows you the contents
of the directory .ssh created in the first step.
• The file “id_rsa.pub” has your public key.
authorized_keys
• In .ssh, you can maintain a file
“authorized_keys” that contains the public
keys of all users you authorize to access
the account, one line per user.
• “cp id_rsa.pub authorized_keys” will
authorize yourself. Then “ssh user@wotan”
will allow you to login again as you on
wotan.
• You can also create a public key with putty.
issuing commands
• While you are logged in, you talk to the
computer by issuing commands.
• Your commands are read by command line
interpreter.
• The command line interpreter is called a
shell.
• You are using the Bourne Again Shell,
bash.
bash features
• bash allows to browse the command history
with the up/down arrow keys.
• bash allows to edit commands with the
left/right arrow keys.
• You can complete command and file names
with <TAB>.
• bash comes with a language of commands
that allows to write batch files.
• “exit” is the command to leave the shell.
environment variables
• These are variables used by the shell.
• Two important ones are
– $HOME your home directory
– $PATH the location where bash will search
for executable files.
• echo $HOME will show you your home
directory.
• “env” is a command that can be used to
see all environment variables.
environment variables and PHP
• All environment variables can be accessed
with $_ENV{'env'} in PHP, where env in the
name of the environment variable.
• Example
$home=$_ENV{'HOME'};
print "my home is $home.</br>";
bash initialization
• Files that start with a dot are hidden. They
are only seen with “ls -a”.
• .bashrc is a file written in bash language
that is run every time bash is started.
• .bash_profile or .profile is run when the
shell is started at login.
• You can customize these files.
files, directories and links
• Files are continuous chunks data on disks
that are required for software applications.
• Directories are files that contain other files.
Microsoft calls them folders.
• In UNIX, the directory separator is “/”
• The top directory is “/” on its own.
home directory
• When you first log in to wotan you are placed
in your home directory /home/username
• “cd” is the command that gets you back to the
home directory.
• The home directory is also abbreviated as “~“
• cd ~user gets you to the home of user user.
• “cd ~” does what?
~/public_html
• Is your web directory. I created it with
“mkdir public_html” in your home directory.
• The web server on wotan will map requests
to http://wotan.liu.edu/~user to show the file
~user/public_html/index.html
• The web server will map requests to
http://wotan.liu.edu/~user/file to show the
file ~user/public_html/file
• The server will do this by virtue of a
configuration option.
changing directory, listing files
• cd directory changes into the directory
directory
• the current directory is “.”
• its parent directory is “..”
• ls lists files
users and groups
• “root” is the user name of the superuser.
• The superuser has all privileges.
• There are other physical users, i.e. persons
using the machine
• There are users that are virtual, usually
created to run a daemon. For example, the
web sever in run by a user www-data.
• Arbitrary users can be put together in
groups.
reason to run things on wotan
• When your run PHP files as a web user, the
web server runs the PHP file.
• The web server runs as a special user,
often called www-data.
• This user is not allowed to create files.
• Since file creation and manipulation is the
essence of digital librarianship, we need to
run directly on the machine.
permission model
• Permission of files are given
– to the owner of the file
– to the group of the file
– and to the rest of the world
• A group is a grouping of users. Unix allows
to define any number of groups and make
users a member of it.
• The rest of the world are all other users
who have access to the system. That
includes www-data!
listing files
• “ls” lists files
• “ls -l” make a long listing. It contains
– elementary type and permissions (see next
slide)
– owner
– group
– size
– date
– name
first element in ls -l
• Type indicator
– d means directory
– l means link
– - means ordinary file
•
•
•
•
3 letters for permission of owner
3 letters for permission of group
3 letters for permission of rest of the world
r means read, w means write, x means
execute
• Directories need to be executable to get in
them.
change permission: chmod
• usage: chmod permission file
• file is a file
• permission is three numbers, first for owner,
2nd for group and 3rd rest of the world.
• Each number is sum of
– 4 for read
– 1 for execute
- 2 for write
- 0 for no permission
• Example: chmod 764 file
general structure of commands
• commandname –flag --option
• Where commandname is a name of a
command
• flag can be a letter
• Several letters set several flags at the same
time
• An option can also be expressed with - and a word, this is more user-friendly than
flags.
example command: ls
• ls lists files
• ls -l makes a long listing
• ls -a lists all files, not only regular files but
some hidden files as well
– all files that start with a dot are hidden
• ls -la lists all files is long listing
• ls --all is the same as ls -a. --all is known as
a long listing.
copying and removing files
• cp file copyfile copies file file to file copyfile.
If copyfile is a directory, it copies into the
directory.
• mv file movedfile moves file file to file
movedfile. If movedfile is a directory, it
moves into the directory.
• rm file removes file, there is no recycling
bin!!
directories and files
• mkdir directory makes a directory
• rmdir directory removes an empty directory
• rm -r directory removes a directory and all
its files
• more file
– Pages contents of file, no way back
• less file
– Pages contents of file, “u” to go back, “q”
to quit
soft links
• A link is a file that contain the address of
another file. Microsoft call it a shortcut.
• A soft link can be created with the
command
• ln -s file link_to_file where file is a file that is
already there and link_to_file is the link.
file transfer
• You can use winscp to upload and
download files to wotan.
• If uploaded files in the web directory remain
invisible, that is most likely a problem with
permission. Refer back to permissions.
• chmod 644 * will put it right for the files
• chmod 755 . (yes with a dot) will put it right
for the current directory
• * is a wildcard for all files.
• rm -r * is a command to avoid.
editing
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There are a plethora of editors available.
For the neophyte, nano works best.
nano file edits the file file.
nano -w switches off line wrapping.
nano shows the commands available at the
bottom of the screen. Note that ^letter,
where letter is a letter, means pressing
CONTROL and the letter letter at the same
time.
emacs
• This is another editor that is incredibly rich
and complex.
• Written by Richard M. Stallman, of GNU
and GPL fame.
• Get an emacs cheat sheet of the web
before you start it. Or look at next slide.
emacs commands
(here ^ stands for the control character)
• ^x^s saves buffer
• ^x^c exits emacs
• ^g escapes out of a troublesome situation
• control+space sets the mark
• ^w removes until the mark (cut)
• ^y pastes
common emacs/bash commands
• ^k kills until the end of the line or removes
empty line
• ^y yank what has been killed (paste)
• ^a get to the beginning of the line
• ^e get to the end of the line
• These commands also work in the shell.
emacs modes
• Just like people get into different moods,
emacs gets into different modes.
• One mode that will split your pants is the
PHP mode.
• “emacs file.php” to edit the file file.php in
PHP mode.
• Then look how emacs checks for
completion of parenthesis, braces,
brackets, and the ; and use the tab
character to indent.
copy and paste
• Putty allows to copy and paste text
between windows and wotan.
• On the windows machine, it uses the
windows approach to copy and paste
• On wotan machine,
– you copy by highlighting with the mouse’ left
button
– you paste using the middle button
– if you don't have a middle button, use left and
right together
creating a PHP file
• To run PHP, edit a file with a name ending
in .php (not required, but useful). Make the
first lines.
#!/usr/bin/php
<?php
/* PHP code goes here */
?>
• The first line less Unix that it has to use
PHP to run this file. The correct path to the
PHP executable has to be given.
running a PHP file
• You must chmod it executable by you, e.g.
chmod 755 my_file.php
• where my_file.php is the name of the PHP
file.
• Then you can run. But you have to give it
the full path.
./my_file.php
running mySQL
• You can run mySQL in command line mode
in wotan. Type
mysql -u user -p
• You will then be prompted for your
password. The username and password
are your mySQL user name and mySQL
password, not your wotan user name and
wotan password.
• Don’t forget the semicolon after each
command!
login to SQL without password
• You can create a special file .my.cnf in your
home directory. In there, write something
like
# this is a file $HOME/.my.cnf
[client]
user = username
password = password
http://openlib.org/home/krichel
Thank you for your attention!
Please switch off machines b4 leaving!