UNIX Commands, Directories, and Processes Assignment

Standard Directories and Files

 In a separate file (use a text editor) cut and paste the commands that you typed (including the prompt) and the complete output of these commands. (show output screenshots also)

Note: The output of the commands should not contain more than six lines.

Please get these 3 files in this assignment which is down below:

1. doc/txt file that cover parts A to E
2. fullname_zombie.c
3. snapshot of top command that shows the zombie process

A. Standard Directories and Files

Directory: contains the names of files and/or sub-directories. Standard directories contain some special files.

Root Directory (/)

The root directory is the top of the file system. It is the master cabinet that contains all folders and files.

1. Get a listing of your root directory. ( use, cd and ls –l)

/bin

The binary directory: contains executable files and most Unix commands.

2. Go to /bin directory. (use cd /bin)
3. List its contents.
4. List 6 commands that you recognize.

/dev

Device directory.

5. Get a listing of the device directory. Do you recognize any device?

/etc

Contains commands and files for system administration. Usually a user is not allowed to change these files.

6. Go to /etc directory.
7. Do a long listing; Mention a few files that you have already heard about.
8. What is the most used permission? What does it mean? (read about permissions in Unix Handout)
9. Using cat, check the passwd file or similar; look for yourself in the file.

/lib

Contains a collection of related files for a given language in a single file called an archive.

/tmp

Contains temporary files.

/etc/passwd

Contains one line for every user on the system and describes that user.

B. Determine the absolute pathname for your home directory

10. Type:

       echo $HOME

11. Type:

      Pwd

C. Shell(s) and Shell Environment variables

1. Check your default shell using: echo $SHELL
2. Use the chsh command and find a list of available shells.
3. Change the current shell to a tcsh .
4. Check your new shell. The change will not be listed until the next login.
5. Use the ps (process status – gives a lists of running processes). What do you observe?

Shell Environment variables

Bourne, Korn shell C shell

CDPATH                    cdpath                                 alias names for directories accessed with cd

ENV                                                                       path along which Unix looks to find config. files

PS1                            prompt                                 shell prompt that appears in the command line

PWD                          cwd                                     name of current directory

HOME                       home                                  the name of the user’s home directory when the user logs

TERM                                                                   type of console terminal being used

D. Processes

Check the Unix Handout and go over the section about Processes -section 17.

The action of each shell, the mechanism of how it executes commands and programs, how it handles the command and program I/O and how it is programmed, are affected by the settings of certain environment variables.

1. Learn about the ps command using man (type man ps)
2. Give a list of possible states together with their significance. Identify your login shell.
3. Type ps –l and explain the significance of: F, S, UID, PID, PPID, C, PRI, NI, ADDR, SZ, WCHAN, TTY, TIME, CMD fields.
4. Use the top command to monitor the CPU activity in real time. It displays the status of the first 15 of the most CPU-intensive task on the system as well as the CPU activity. To stop the execution of top enter <ctrl-C>.
5. Give the total number of tasks, number of running processes, sleeping processes, stopped processes and zombies.
6. Identify the shell process. Use the “regular” kill command to terminate the shell.
7. Use the “sure kill” command to terminate the shell. Explain.

Part E

1. Use Internet sources and give an overview of the command that is used in Windows for creating a process.

2. In a Unix environment, execute parent.c, child.c and orphan.c as follows:

Note: upload first the 3 files in your venus home directory.

child and parent:

- compile the child and parent:

gcc parent.c –o parent

gcc child.c –o child

- run the parent in the current directory (the parent after the fork will call the child)

Don’t worry about warning messages.

./parent

orphan:

- compile and run the orphan:

gcc orphan.c –o orphan

./orphan

Observe and understand the programs’ execution output.

Extensively comment the output of the programs by relating the theory discussed in class, the meaning of the covered commands and the program listings.

3. Write a very simple program that will show the possibility of having zombie processes.

Write a program named zombie.c

The main process will create a child.

The child prints something like: “I am the child with pid ….. and my parent has ppid ….”

Next, the child will sleep for 1 second.

Child exits.

The parent will print: I am the parent and my id is… Next, the parent sleeps for 30 seconds. Since the child ends first, and the parent didn’t do wait( ), the child will be for a while in the zombie state. Run the parent in the background, so you can use the top command and identify the zombie, before the parent terminates.

Note: even if the parent terminates, the child is still a zombie. However the the init process reaps the zombies frequently.