IT 244: Introduction to Linux/Unix
Class 27

Today's Topics


New Material


There will be no graded quiz next week.

Final Exam

The final exam will be given on Tuesday, December 19th from 3:00 - 6:00.

The exam will be given in McCormack 3-430.

There will be 50 questions, which will be similar to the questions on the mid-term and the quizzes.

As with the Mid-term, 60% of the questions will come from the ungraded Class Quizzes.

The questions will cover all of the material for this course.

The last class, Tuesday, December 12th, will be a review session.

You will only be responsible for the material contained in the Class Notes for that class, and the Class Notes for the review session for the Mid-term, which you will find here.

Although the time alloted for the exam is 3 hours, I would expect that most of you would not need that much time.

You will not be able to leave the room until you turn in your exam paper so you should visit the restroom before you take the test.

The final is a closed book exam.

Today's Class

There will be no Class Quiz today.

The new material we cover today will not be on the final.

Instead, I'll talk about some advanced features of Linux/Unix that you should be aware of.


Using Braces, { } , with Variables

Special Parameters

$ - The PID of the Current Shell Process

! - The PID of the Last Process Put into the Background

? - The Exit Status

Positional Parameters

# - The Number of Command Line Arguments

0 - The Pathname of the Script

1 - n - The Command Line Arguments

New Material

Expanding Null and Unset Variables

:-- Use a Default Value

:= - Assign a Default Value

:? - Displays an Error Message

The [[ ]] Command

&& and || as Command Separators

An Introduction to AWK

Running awk

AWK Syntax

Blank Pattern

Regular Expression Patterns

BEGIN and END Patterns

Comparison Patterns

The comparison pattern will cause its action to be performed when it is true:

Range Patterns

AWK Fields

Class Exercise 27

Today's Class Exercise is unusual.

I am asking you to recreate the script I used to test Class Exercise 25.

Let me explain how this script works.


Class Quiz