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Linux Shells by Example: Chapter 1 Reading Guide
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-IAN! idallen@ncf.ca

Here is a reading guide and some review questions for Chapter 1
"Introduction to Linux Shells".  (You already answered most of these
questions; most of this guide is copied from the Week 2 notes file.)

*)  What are "tokens" to a shell?  What delimits tokens on a command line?

*)  Does a shell script need to be compiled first?

*)  True or False: the shell verifies your password at login.

*)  Where does the shell search for a command name?

*)  Which happens first, quote processing or variable substitution?

*)  If there is an alias named "foo" and an executable program named
    "foo", which will be executed by the shell?

*)  What is a process?

*)  What is a "system call"?
    Name the three major system calls used by shells to run commands.

*)  What is the "fork" system call?  "exec"?  "wait"?   "exit"?
    Match them to these descriptions:
        ?) overlays the current process with another program
        ?) suspends processing until a child process finishes
        ?) duplicates the memory of the current process (makes 2 processes)
        ?) causes the current process to terminate

*)  Name some things in the shell "environment" that are passed to
    child processes.

*)  What is your process "umask"?  How is it used?  Is it passed to
    child processes?

*)  Before the umask is applied, what default permissions would be
    given to a new directory?  to a new file?

*)  If you create a new file, change your umask, and then copy an
    existing file onto the new file, what happens to the permissions of
    the new file?

*)  How do octal permission numbers (e.g. 755) relate to rwx style
    permissions?  How do you express "chmod 755 foo" using symbolic
    (letter) permissions?  How do you express "chmod u=r,g=w,o=x foo"
    using octal permission numbers?

*)  Can ordinary users (non-root, non-super-user) use the "chown" command?

*)  What is your "working directory"?

*)  What is the difference between your home directory and the
    Unix directory that has the name "/home"?

*)  If a child changes directory, does it affect the directory of the
    parent process too?

*)  What is the difference between a local and an environment variable?

*)  If a child changes an environment variable, does it affect the variable
    in the parent process too?

*)  What are "stdin", "stdout", and "stderr"?  To what are these
    attached when you first log in and get a shell prompt?

*)  What is "redirection"?  Can I redirect stdout and stderr separately?

*)  What is a "pipe"?

*)  Explain the difference (if any) between these command lines:

    $ date | wc
    $ date > wc
    $ date < wc

*)  What do most "signals" do to a process?
    [the book is wrong about signal 0 on p.29 - see the textErrata.txt file]
    NOTE: Signal numbers and names may change from one version of Unix to
    another, especially signal numbers above 15.  Don't memorize them.
    Most Unix systems agree on these numbers: HUP INT QUIT KILL and TERM

*)  What key sequence usually generates a SIGINT (interrupt) signal?

*)  What key sequence usually stops a process (SIGTSTP), so that it
    can be restarted later using "bg" or "fg"?

*)  What is a shell script?  How do you create one?

*)  True or False: The VI editor automatically makes shell scripts
    executable when you write them out.

*)  True or False: You can always execute a script named "foo" by just
    typing "foo" at the shell prompt.

*)  True or False: The first line of every shell script should contain
    the absolute pathname to the shell that will interpret the script,
    e.g. #!/bin/bash or #!/bin/csh, etc.