1. Learn how to turn in your assignment.
2. Use several UNIX commands discussed in the Lab 1.
3. Create, compile, and run a C++ program.

This is not a test.  Try to do the exercises on your own, but if you get stuck, ask for help.

1. pico (try  typing "man pico" at the UNIX prompt)  (a similar editor available in Cygwin and Linux is nano)
   
2. vim (new version of vi editor)  Vim Homepage  works on most UNIX and microsoft platforms.
3. emacs GNU's emacs page works on most UNIX and microsoft platforms

pico is like riding a tricycle.  It is easy to learn, but neither fun or powerful.

vim and emacs are like a bicycle.  Hard to learn at first, but one you know it, much faster than a tricycle.

Many students never learn vim or emacs, and spend years editing at tricycle speeds.

For now, you might want to stick to pico, but I recommend that at some point this semester you learn to use either emacs or vim.

There are 3 levels of file protection in UNIX: owner, group, other

You can set 3 types of permission for each level: read, write, execute

read == can read the file
write == can write the file
execute == if it is a directory, can cd to the directory
                  if it is a file, can execute a file (not all files can be executed)

An integer is used to describe each level of protection.  Thus file permissions can be described by three integers

    one integer for the owner
    one integer for the group  (each file has an attribute which names which group it belongs to)
    one integer for the other

Since there are 3 levels of permission (read, write, execute) described by each of these integers, we need an encoding method.  That method is as follows

if the file is executable, add a 1 to the number
if the file is writable, add a 2 to the number
if the file is readable, add a 4 to the number

Q1: Why doesn't chmod  use, 1, 2, 3  instead of 1,2,4?  What is special about 1,2,4? answer

Thus if you want a file to be readable and writable by the owner, you set the owners protection to 6 (2 + 4) using the chmod command.

    $ chmod 600 lab1.cpp

The three integers passed to chmod represent the owner, group, other numbers.  In the above example, the group and world have no access to the file lab1.cpp.

Here are the most common file protections:

$ chmod 644   the owner can read/write, the group and world can only read
$ chmod 755   the owner can read/write/execute, the group and world can read and execute
$ chmod 700   the owner can read/write/execute, the group and world have no access
$ chmod 600   the owner can read/write, the group and world have no access

(1) Create a directory for your 112 labs.  You may choose the name and structure.  Here are some suggestions (remember that the ~ stands for your home directory).

• ~/classes/112/labs/lab1  ~/classes/112/labs/lab2 ...
• ~/classes/112/labs/1  ~/classes/112/labs/2 ...
• ~/112/labs/lab1 ~/112/labs/lab2 ...
• ~/1  ~/2 ...     (this is a joke, these names in your home directory would not be very meaningful)

      Hint:  use mkdir to create a directory.  You have to create each directory along the way.   For example,
      if you choose ~/classes/112/labs/lab1 as your naming convention, you have to call mkdir 4 times.

(2) Protect your new directories so no one else can look at them

In UNIX, if you protect a directory, all the files in that directory and the subdirectories are also protected
In the first example above, you could change the protection of  ~/classes

You will need to use the command chmod (see above).

Recall that you must set the permission of a directory to executable if you want access.

Q2: What number do you want to pass to chmod so only you can read this directory? answer

Q3: What command can you use to find out how to use chmod? answer

In your directory for lab 2, create the file hello.cpp (using any text editor, pico is the easiest to use).  Edit hello.cpp so it contains the following text.

#include <iostream>

using namespace std;

int
main()
{

cout << "hello world" << endl;
return 0;

}

Don't use cut & paste, I want you to practice using the editor.

Compile this file using the command:

$ g++   hello.cpp

if you got an error, use the editor to fix the error

This should have created the file a.out, use "$ ls -l" to find out if a.out is in your directory.  Notice that a.out automatically has executable protection.

Run your hello program.  You can execute the program by typing a.out at the UNIX prompt. 

$ a.out

     If a.out doesn't work, try ./a.out and ask for help fixing your environment so you don't need the "./".

Run your hello program and redirect the output to the file hello.out using the shell's redirection symbol > (see lecture notes from lab1 for the redirect systax)

You can view hello.out using an editor or the cat command (cat simply writes the files passed to it to standard output).

    $ cat   hello.out

Modify your program to prompt for and read a user's name as follows.

#include <iostream>
#include <string>

using namespace std;

int
main()
{
	string name;

	cout << "What is your name? ";
	cin >> name;
	cout << "hello " << name << endl;
	return 0;

}

Compile and run this program (using the same g++ command above).

Now create a file with a name in it (call it name_file).  You can do this using an editor such as pico.

Using redirection, read from this file and write to another

$ a.out < name_file > hello.out

Check the hello.out to make sure it is correct.

Q4: What UNIX command deletes a file? answer

Delete the file: hello.out

Execute the following command:

$ man -k remove

What happened?  Too fast?  try:

$ man -k remove | less

There are 211 entries, sometimes this trick doesn't work?

How do you think I figured out there were 208?  There is a program that counts lines, words, and characters called wc.

Q5: How could you take the output from man and pass it to wc? answer

How many entries are there for permission

      $ man -k permission