IT 244: Introduction to Linux/Unix
Class 17

Today's Topics


New Material

Reading Assignment

You should have read chapter 8 of Sobell, The Bourne Again Shell.

Homework 8

I have posted Homework 8 here.

As usual, it will be due next Sunday at 11:59 PM.


Let's review the answers to the Mid-term.

Your Current Standing in This Course

If you want to know your grade as of this moment, send me an email.

In performing this calculation, I will assume that your score on the final exam will be the same as that of you mid-term score.

I can do this only for your grade as of the mid-term.

I can't do this for your grade later in the semester.


Pathname Expansion

The ? Meta-character

The * Meta-character

The [ and ] Meta-characters


Help for Built-ins

Different Shell Versions

Using a Different Shell


Shells For Running Scripts

Ways a Shell Can Be Created

Your Login Shell

Interactive Non-login Shells

Non-interactive Shells

Creating Startup Files

New Material

Running a Startup File after a Change has been Made

Commands that are Symbols

( ) Runs whatever commands are enclosed in the parentheses in a sub-shell
$( ) Command substitution:
runs the commands enclosed in the parentheses in a subshell and returns their value to the command line, replacing the dollar sign, the parentheses and everything in them with this value
(( )) Evaluates an arithmetic expression:
by default, Unix treats everything as text, but this command evaluates whatever it encloses as a numerical, rather than a string, expression
$(( )) Arithmetic expansion:
evaluates an arithmetic expression and returns its value at that place on the command line
[ ] The test command:
used to evaluate a boolean expression in constructs like if clauses
[[ ]] The conditional expression:
similar to [ ] but adds string comparisons

File Descriptors

Redirecting Standard Error

Shell Scripts

Making a Shell Script Executable

How Unix Runs a Program

Running a Shell Script

Specifying Which Shell Will Run a Script

Comments in Shell Scripts


Class Quiz