COP 3353: Review Checklist of Topics Covered (since Midterm)

This is a list of topics intended as a checklist to help you recall what topics and commands have been covered. To be fully prepared for the final WHICH IS CUMULATIVE, know the topics here, as well as the topics for the first midterm.

Process Management

Multitasking and multiprocessing
Processes
- run in their own memory and address space
- multiple processes scheduled to run on same processor (by the OS)
Creation of processes in Unix - just know generally
- A parent process creates a new process with the fork command
- New process a clone of the parent at first
- Child process makes an exec system call to start up a new program on the process
- ALL processes in Unix created this way, starting with one initialization process when a system is booted
Job control commands can be used to view, manipulate, and halt processes in a Unix system
- ps, jobs, kill, fg, Ctrl-C, Ctrl-Z
- Use & to launch a process as a background job

Shell Commands Covered

Command	Description	Flag options covered	You should be able to
`grep`	Search for patterns within files	`-i -n -l -P`	ignore case line numbers display filenames only
`ps`	report on current processes	`-e -f -a aux -l`	view all processes on the system (-e) view the "full format" (-f) all processes except for session leaders (-a) view the "long format" (-l)
`jobs`	Shows background processes		view the current background processes you are running
`fg`	put a job into foreground		put one of your background processes into the foreground
`bg`	run a job in the background		put one of your current jobs to run in the background
`Ctrl-Z`	suspend the current foreground process		suspend a process without killing it
`Ctrl-C`	kill foreground job		kill, or cancel, the current foreground process
`kill`	kill a running process, through its process ID (PID) number	`-KILL or -9`	send a KILL signal to override and halt processes that can't be killed with normal kill command
`sleep`	a delay for a specified time		cause current process to sleep, or delay, for specified number of seconds
`sh`	Run the Bourne shell		start the Bourne shell (no parameters) or run a script with `sh` (one parameter)
`bash`	Run the Bourne Again shell		start the Bourne Again shell (no parameters) or run a script with `bash` (one parameter)
`csh`	Run the C shell		start the C shell (no parameters) or run a script with `csh` (one parameter)
`tcsh`	Run the Tenex shell		start the Tenex shell (no parameters) or run a script with `tcsh` (one parameter)
`ksh`	Run the Korn shell		start the Korn shell (no parameters) or run a script with `ksh` (one parameter)

Shell Scripting

Basics

Know how to set up a script to run as an executable
- Setting permissions on the file
- #! mark as first line of file, specifying what shell
Know how to run a script with a shell command
- Use shell command, with script as parameter
- Script file only needs be readable (not executable) for this
- Ex: tcsh script1
Basic commands frequently used in scripts:
- exit: quits the script
- echo: prints lines to standard output
Environment variables
- Can look them up in current login shell with env command
- Can access their values in a script with variable de-reference $
  Ex: echo $HOME # prints value of HOME variable
General variables in shell scripts
- Know how to create them in tcsh (using set command)
- Know how to create them in sh or bash (just name and assign value)
- Know how to de-reference a variable to get its value (uses $ symbol)
read command
- Know how to use read to get data into a variable from standard input
- Can be used for keyboard input
- Also can re-direct data in from a file, using input redirection symbol
Shell arguments
Know the special meaning of these de-reference symbols:
- $1, $2, etc through $9 and $0
- $#
- $@
Quoting rules
Know the effect of double quotes and single quotes (and their difference), specifically on special characters
Exiting with a status
- exit just means end the script
- exit 0 ends the script and sends back the "good" status of 0
- Can also exit with an error code (non-zero) as a status

Control structures in scripts

Conditionals
Know how to test a condition
- Reverse a comndition with ! before the condition
- [ : ] always true
Common condition tests
- Know how to test an argument to see if it is a file or a directory
- Know how to test a file/directory for readability, writability, executability (for whoever runs script)
- Know how to do numeric tests in a script (-eq, -ne, -gt, -ge, -lt, -le)
- Know how to test strings with =, !=
- Know how to test strings with <, <=, >, >=
- Know how to combine conditions with && and ||
if statements
- Know the general form of the if statement
- Understand the placement of the syntax elements then, elif, else, fi, and the condition, in an if-statement
case statements
- Know how the basic case statement works, to match a string against a list of possibilities
- Syntax words: case, in, esac
while and until loops
- Understand how these loops work, and use a true/false condition as a test
- Know the placement and use of syntax elements: while, until, do, done
for loops
- Know how to use a for-loop to range a variable through a list of values
- Know how to use wild-cards to range the variable through filenames in your file system
- De-reference variable inside loop with $

Other scripting tools

Command Substitution
- Know how to use the backquotes ` ` to do command substitution
- Understand the result that comes from using this in a script
Checking exit status
Know how to have one script call another, and check the exit status of the script it called
expr command
- Know how to use the expr command to do basic arithmetic and comparisons
- Understand how to combine this with command substitution to store arithmetic results into script variables
- Example: Understand how to use expr and command substitution to increment a counter, as in the last assignment