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Week 03 Notes for NET2003
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-Ian! D. Allen - idallen@idallen.ca - www.idallen.com

Remember - knowing how to find out an answer is more important than
memorizing the answer.  Learn to fish!  RTFM!  (Read The Fine Manual)

Review
------

    1   bash
    2   cal (9 1752)
    1   cat (-s)
    1   cd
    1   cp (-u)
    1   date
    1   dir (DOS alias - use ls instead)
    1   echo (shell built-in and external)
    2   exit (shell built-in)
    2   ifconfig
    1   less
    1   ls ( -l -a -d )
    1   man (-k)
    1   more
    2   mv
    2   passwd
    1   pwd (shell built-in and external)
    2   rm ( -r -f )
    2   sort (-n -r -u)
    2   stty ( erase '^H'  erase '^?' )
    1   vi, vim  (-r)
    2   wc ( -l -w -c )
    2   wget [-O outfile] {URL}
    1   which
    1   who

Q: What is the output on your screen of "sort foo foo" if foo contains:
   2
   22
   11
   1

Q: How do you tell sort to sort by number?  sort in reverse?

Q: How do you fetch the file at URL http://tc.ca/ into your current directory?

VIM Tips
--------

 - Multi-window multi-file editing: :split, :vsplit, :qall, ^W
   For help in VIM type    :help ^W

Linux basics - continued
------------

Unix directory tutorial:
  - http://www.ee.surrey.ac.uk/Teaching/Unix/unix1.html
  (but note that they incorrectly give the ROOT directory a name of "/")

The Unix Shell (e.g. "bash" - Bourne Again SHell)
 - Notes: shell_basics.txt - The Unix/Linux Shell
 - purpose of a shell is: to find and run commands
   - with some support for programming (scripts)
   - you can use ";" to separate multiple commands, e.g.:
     $ sleep 4 ; echo BOO
     $ date ; date ; date
     - in shell scripts, avoid using ";" - put each command on its own line
 - shell is an unprivileged program
   - standard Linux shell is named "bash"; you can start up multiple
     copies of bash by typing its name as a command
   - type "exit" to cause a shell to terminate
 - shell prompts when it reads from your keyboard
   - shell does not prompt if reading input from a file!
   - most other Unix programs do *not* prompt when they read your keyboard
   - Notes: shell_prompt.txt - Setting the BASH shell prompt
 - shell splits your command line on blanks (white space)
   - first non-redirection word is the command name
   - the rest of the arguments are passed to the command
   - Notes: arguments_and_options.txt - Options and Arguments on Command Lines
 - shell can expand file GLOB patterns (similar to DOS wildcard)
   - shell helps with wildcards (GLOB)
   - * matches zero or more characters
   - ? matches a single character (any character, even a space)
   - [abc] matches a single character from the list abc
   - like ls, GLOB patterns never match names that start with a period (hidden
     pathnames), unless you explicitly put a real period at the start
   - echo *     - does not match hidden files
   - echo ?*    - does not match hidden files
   - echo [.]*  - does not match hidden files
   - echo .*    - matches only hidden files (pattern starts with a real period)
   - Notes: glob_patterns.txt - GLOB patterns (wildcard pathname matching)
 - shell can expand variables, both local and environment
   - e.g. you can see a $variable as in:   echo "$SHELL"
   - the shell does the variable expansion, not the command!

Searching for text inside files:
    $ grep 'pattern' [files...]
  - crude Data Mining: selecting content by looking for lines
  - searching for keywords in the course notes:
    $ grep 'ssh' ~idallen/public_html/teaching/net2003/08w/notes/*.txt
 - the grep -v option finds lines that do *not* contain the pattern
   - similar in behaviour to the g// and v// commands in VIM

Course Notes to read
--------------------
    arguments_and_options.txt
    glob_patterns.txt
    miscellaneous.txt
    shell_prompt.txt
    unix_command_list.txt

============================================================================

Q: What is the main purpose of a shell program?

Q: T/F any program that wants to read from your keyboard will prompt
   you for input

Q: T/F the number of extra blanks between arguments on the shell
   command line doesn't matter - one blank is the same as twenty

Q: Describe how GLOB patterns work in the Unix shell.

Q: Describe how to stop the shell from splitting text at blanks
   (e.g. a file name with blanks in it)

Q: T/F shell GLOB patterns *never* match leading periods in names

Q: T/F "echo [.]*" matches all hidden file names

Q: T/F In the command "echo *" it is the "echo" command that expands the "*".

Q: T/F In the command "ls *" it is the "ls" command that expands the "*".

Q: T/F In the command "echo $SHELL" it is the "echo" command that
   expands the $SHELL variable

Q: What type of pathnames does "echo */." output?

Q: What type of pathnames does "echo ./*" output?

Q: How do I search for text in a directory full of files?