Agenda Administrative Issues Link of the Week Review Week Two Information This Week’s Expected Outcomes Moving around in UNIX Break-Out Problems Upcoming Deadlines Hands-on Information Lab Assistance, Questions, and Answers

Administrative Announcements The midterm and the final exam are both electronic. Please verify that your testing facility can administer this type of test. The Student Learning Center has been requested to send midterm exams to your proctors. They will me within a couple days that the request has been completed.

Link of the week Data Disaster Ontrack Data Recovery Data recovery Knoll Ontrack is one of the worlds largest data recovery services. They have performed more than 500K data recoveries since 1985.

Link of the week Data Disaster Rescuers CompuRecovery found on the Internet for desktop hard drive recovery. Datarecovery.com 7/24 found on the Internet. Provides RAID, hard drive, and laptop data recovery solutions. Norman Ken Ouchi at IBM was awarded the patent in 1978 for the recovery of data stored in failed memory unit. Later developed into RAID 10.

Link of the week Data Disaster 1. Big and small company operations 2. Backup services off site location and media. Test data occasionally 3. Trouble shooting

Link of the week Ironkey USB Flash Drive Data Disaster Helpful Hints - Use dedicated circuits for your connection - Keep your computer cool and in a dry place - Use a UPS (Uninterrupted Power Supply) - Don’t assume that your data is permanently destroyed even if the situation looks bad - Secure your work area and devices

Course expected outcome Learning Outcomes (Week five) Write Perl scripts, including variables, control flow, and regular expression syntax

UNIX Operating System Process and multitasking The UNIX kernel can keep track of many processes at one time, and dividing it’s time to other system tasks. Each process submitted to the kernel is assigned a unique process ID (PID). In every version of UNIX, the PID range is 0 through and is restrained to 5 digits.

UNIX Operating System Single-tasking operating systems only perform one task at a time. The user of a single-tasking system can switch from one window to another window, executing a different application, but only one task is ever active at a time. When a user switches from one window to another window, the switched task that is left, is suspended, until the user switches back to it. Suspended tasks are not allocated system resources, but remain as it was when it was suspended. When a suspended tasks resumes execution, it starts where it left off, as if nothing ever occurred.

UNIX Operating System Killing processes At times a process must be terminated prior to its normal intended completion. The UNIX shell provides a utility named, kill to end the execution of a process. Prior to issuing the kill command to terminate a process, the processes PID must be determined by using the ps –f command. The kill command is also used to send a preparatory signal(s) to an executing process prior to receiving a termination signal. A process can only be terminated by the owner of the process or by root. The syntax format for the kill command is as follows: kill [-options] process-ID

UNIX Operating System Parent and child processes Each UNIX process has two unique numbers associated with them. One is the Process ID (PID) and the second one is the Parent Process ID (PPID). All user processes in the system has a PPID, except for the init process, which will be addressed in the course boot-up procedure.

UNIX Operating System Orphan and zombie processes Normally, when a child process is terminated, the parent process receives a SIGCHLD (code 17) signal from the kernel. After the parent receives the SIGCHLD signal, the parent can perform any last minute task or restart a new child process prior to the termination of its child. However, if the parent is terminated prior to its child process, the child process is left without a parent. If this situation occurs, the child process becomes an orphan and the init process becomes its new parent process. The orphan process will then be assigned a PPID of 1.The term used to best describe the init processes action is re-parenting.

UNIX Operating System When a process is terminated, but still displays its presence on the system in a Z state. This is a zombie, or defunct process on the system. A zombie is a process that completed execution, but is dead. It does not consume system resources. It retains an entry in the process table. A good process display command is ps –aux.

UNIX Operating System Daemon process A daemon process is often a system related background process. Normally, a daemon process comes into being during boot-up and terminates when the system is rebooted or shutdown. A daemon process is not attached to a terminal like a foreground process. Verification of this attribute can be observed by performing the ps –ef command, and observing the tty field, all daemon processes display a ? in this field.

UNIX Operating System Daemon processes execute in the background and few know that they exist. Daemons execute waiting for data to be passed to them from some application, such as, a database, network, or printer daemon waiting for a print command. Daemon processes normal are known as service providers.

UNIX Operating System Top command The top command is a useful tool for displaying processes sorted by various criteria. It is an interactive tool that updates frequently and displays data about physical and virtual devices, CPU usage, and load averages.

UNIX Operating System Finger command The finger command displays information about users on a specific host. Local host finger Obtain specific information on a user on a local machine: finger dandrear View all the logged in users on a remote machine: Get information about a specific user on a remote machine finger

UNIX Operating System Umask Calculation umask setting = 027 Complement of umask = 750 File default permission setting = 666 Directory default permission setting = 777 The resultant permissions are calculated via bitwise AND of the unary complement of the argument (using bitwise NOT) and the permissions specified by the program.

UNIX Operating System Regular Expressions Definition: Regular expression provides a concise and flexible means for "matching" (specifying and recognizing) strings of text, such as particular characters, words, or patterns of characters. Abbreviations for "regular expression" include "regex" and "regexp". The concept of regular expressions was first popularized by utilities provided by Unix distributions, in particular the editor “ed” and the command/filter grep. Example: if ( /UNIX V5/ ) { print “UNIX V5 found on system. \n”; }

UNIX Operating System Regular Expressions Substitution operator: s/original value/new value/ Character class: Matches a single character that is contained within the brackets [ a-zA-Z0-9_ ] Special or meta characters are used to denote actions or delimit groups: + means “one or more of whatever was before the + symbol”. Matches any single character (i.e., x.z) ^ Matches the starting position within the string $ Matches the ending position of the string or the position just before a string-ending newline

UNIX Operating System Regular Expressions

UNIX Operating System

What is ELF? Executable and Linking Format (ELF) is a common standard file format for executables, object code, shared libraries, and core dumps.

UNIX Operating System Perl Syntax ;End of statement delimiter,Comma for line continuation \nNew line (non-printable character) <>The "diamond operator", <> is used when a program is expecting input, but isn't concerned how it arrives.

UNIX Operating System Perl Syntax $ Singular variables prefix (single value, number or Prefix for plural variable (array) %Prefix for plural variable (hash) $_ Default variable It Is the "it" variable. It's often the default parm that built-in functions use, or return into. $0Contains the name of the program being run

UNIX Operating System Perl Syntax while ( … ) { Action statements } What is a continuous loop? while ( 2 ) { Action statements }

UNIX Operating System Perl Syntax The Perl language does not support case or switch statements. The closest way to achieve case evaluations is as follows: if ( $condition_one ) { action_one (); } elsif ( $condition_two ) { action_two (); }... elsif { action_n (); }

UNIX Operating System Three Types of for loops # Old style C for loops for (my $i = 0; $i < 10; $i++) { $array[$i] = $i; } # Iterating loops for my $i { print "$i\n"; }

UNIX Operating System Three Types of for loops (continued) # Postfix for loops print "$_\n"

UNIX Operating System Perl Syntax foreach $total (12,9,3,7) { # Sum each value in the list. $sum += $total; }

UNIX Operating System Perl Syntax foreach (-32,10,1,2,0,-1) { # Valid numbers are considered to be greater than zero # The default variable is utilized, if ( $_ > 0 ) { # Print each valid number on a single output line. print "$_\n"; }

UNIX Operating System

Open Statement The open function can be used to create file handles for different purposes (input, output, and piping), you need to be able to specify which behavior you want. When you open a data file in Perl, all you have to do is specify (a) a file handle and (b) the name of the file you want to read from. open (CHECKBOOK, "checkbook.txt");

UNIX Operating System Open functions open(file_handler, “file_name”) open(file_handler, “<file_name”) open (file_handler, “>file_name”) open (file_handler, “>>file_name”) See page 21 in your Perl text.

UNIX Operating System Filehandle is utilized for both input and output files. Most file names are cryptic and are meaningless to programmers. The purpose of a filehandle is to help the programmer remember a simple file name throughout a program. A filehandle is a name given for a file, device, socket, or pipe. Filehandle command line format: open(filehandle, file name, permissions, chmod); Example: open($FH,$file_name);

UNIX Operating System If you want to read text from a file line-by-line, then use the following syntax: = ; The operator - where FILE is a previously opened filehandle - returns all the unread lines of the text file in list context or a single line in scalar context. Hence, if you had a particularly large file and you wanted to conserve memory you could process it line by line: while ( ) { print $_; }

UNIX Operating System What is List = (6 - 4, 4 * 4, 8 / 2, 9 - 8); while ( … ) { … }

UNIX Operating System What is List = (6 - 4, 4 * 4, 8 / 2, 9 - 8); while ( … ) { … } Perl's for loop, or for statement, is used to loop through a designated block of code until a specific condition is met.

UNIX Operating System What is a “for” loop? for (counter = 0; counter < 10; counter++) { … } Three expressions are contained in a for loop: 1. Set initial state of the loop variable 2. Condition test the loop variable 3. Modify the state of the loop variable

UNIX Operating System foreach Statement Format foreach VAR (List) { … }

UNIX Operating System foreach Statement = ('Larry', 'Curly', 'Moe'); foreach { print $_; }

UNIX Operating System Perl Program Statement #!/usr/bin/perl #!/usr/bin/perl –w

UNIX Operating System Print continuation statement print "error: incorrect number of arguments", "\n", "usage: intlist a b (where a < b)", "\n";

UNIX Operating System Points of interest Online Documentation Websites that have Perl documentation. The two biggest ones are: for modules

UNIX Operating System Demonstrate Perl script:./array_display.pl./array_sort.pl./diamond_oper.pl./perl_it.pl and perl_loop.pl./read_list.pl./sum_list.pl./linenum.pl and./intlist.pl

UNIX Operating System Moving Around in UNIX cal –y (display a calendar for the year) cal –j 2010 (display Julian dates) cal –m 2010 (display Monday first day) cal –s 2010 (display Sunday first day) cal (display September 2010 month

Break-out problems Define a Perl hash table Define ELF Define a Perl array What convenience does a Perl filehandle provide? What is the functionality of a regular expression? Are continuous loops useful? Define an object file Define common-arrow Perl default variable Perl “it” variable Explain the s/pattern/new version/ command

Hands-On-Information Lab Assignment 4-1, Simple Perl Scripting, due February 3, Lab Assignment 5-1, Makefile Exercise, due February 17, Lab Assignment 6-1, Programming Assignment 1, due February 24. Read Chapters 3 and 4 in Essential System Administration text. Read Module Three listed under the course Web site. Everyone should have received a Perl Quick Reference document and script logic for Lab Assignment 5-1 and 6-1.

After class assistance Questions? Comments? Concerns? After each Franklin Live session, I will remain on the session to provide assistance unless otherwise indicated.

Lab Assistance available by phone and/or