1. CHAPTER 8 (skip 299-310, 333-354) CHAPTER 10
John Carelli, Instructor Kutztown University

2. Interactive login shell
First shell to provide a prompt upon login
Executes the following in order
/etc/profile
.bash_profile
.bash_login
.profile
Interactive nonlogin shell
When a new terminal is opened
only executes .bashrc
source filename
execute commands in named file
OR execute it as a shell script (next)

3. Shell Scripts (again)
Shell Script: an executable (text) file that contains shell commands.
When the shell script is run, the commands in it get executed
bash script
#!/bin/bash
Must be executable
# comments
execution in current shell with . (dot)
changes to variables persist in current shell
ex: testvar

4. Variable name Assignment Display Array variables Declare statement
 $
Array variables
 ${name[*]} … or
 ${#name[*]} … or
 ex: arrayvars
Declare statement
declare varname
declare –r varname # readonly – like const
unset

5. Single quote '
Double quote “
Backslash \
metacharacter “escape”
Back quote `
command substitution
ex: quotescript

6. alias
unalias
Quotes in aliases
only matters if alias contains a command substitution
single: substitution occurs when executed
double: substitution occurs when created
ex: aliases

7. Arithmetic Expressions
Double parenthesis
evaluate an arithmetic expression
syntax:
(( arithmetic expression ))
(( z = x + y ))
Can drop $ in variable names
ex: arith

8. Operators if – then - fi if-else elif ex: operators Test and []
Arithmetic
Relational
String comparison -n -z
File testing
if – then - fi
if-else
elif
ex: operators

9. Control Statements while for until break continue ex: looping case
select
ex: menu
(see also: getopt) 8

10. Command-line arguments shift ex: shifting$#
Number of positional parameters $$
PID $?
Exit status of most recently executed command $0
Program name
$1 - $n
Positional parameters $*
All positional parameters

11. Definition
Arguments
return
export
there is no scoping – variables are global
except for cmd line args (can’t change those)
ex: functest

12. type
read
exec
trap