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DAT2330 Test Four B - Unix - Questions
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-IAN! idallen@ncf.ca

You will need to be running Floppix with networking to do this
test.  You must have network access to use telnet and ftp to
reach the machines mentioned in this test.

Your directory test_four is where you must put your scripts and
your script output if you want the instructor to mark them.  This
directory will be created by your instructor before you start
your test.  Your scripts do not have to create this directory;
you may assume it exists any time a script specification requires
you to use it.

Only scripts and output found under directory test_four on the
Test Machine will be marked.  Only correctly-spelled script and
file names will be marked.

Your scripts must start with a valid Script Header, as given in
class and in the Week 7 notes.	Scripts without a valid header
will be penalized.

Scripts containing useful comments will earn bonus marks, to a
maximum of five marks per script.

Problem A - Marks: 50
On the Test Machine: Write an executable shell script named
compdater.sh that will do the following actions (in the order
given below):
  1. [Marks: 6] Verify that there is exactly one command line
     argument; otherwise, exit with an error message.  (i.e. Exit
     if there is not exactly one argument.)
  2. [Marks: 2] Put the first argument into a variable named
     cprog.
  3. [Marks: 5] Verify that the path named by the cprog variable
     is a file; otherwise, exit with an error message.	(i.e.
     Exit if the path is not a file.)
  4. [Marks: 5] Verify that the file named by the cprog variable
     is readable; otherwise, exit with an error message.  (i.e.
     Exit if the file is not readable.)
  5. [Marks: 5] Verify that the file named by the cprog variable
     is not empty; otherwise, exit with an error message.  (i.e.
     Exit if the file is empty.)
  6. [Marks: 2] Put the current date into the file myerrs.txt in
     the current directory.  Exit with a non-zero exit status if
     the command fails.
  7. [Marks: 8] If the file named by the cprog variable contains
     the 6-character string <stdio then compile the file using
     the C language compiler.  Name the compiled output program
     mycout. Turn on all warnings during the compile.  Append any
     error or warning messages that may be generated on standard
     error by the C compiler to the myerrs.txt file.
  8. [Marks: 8] If the file named by the cprog variable does not
     contain the 7-character string printf( then compile the file
     using the C++ language compiler.  Name the compiled output
     program mycppout. Turn on all warnings during the compile.
     Append any error or warning messages that may be generated
     on standard error by the C++ compiler to the myerrs.txt
     file.
  9. [Marks: 9] If the file myerrs.txt contains less than two
     lines, remove it; otherwise: (1) rename it to be myerrs.dat,
     (2) display the contents of the file with line numbers, (3)
     change the file's permissions to be read-write for the owner
     and group of the file and nothing for anyone else.

Problem B - Marks: 58
On the Test Machine: Write an executable shell script named
differ.sh that will do the following actions (in the order given
below):
  1. [Marks: 6] Verify that there are more than zero command line
     arguments; otherwise, exit with an error message.	(i.e.
     Exit if there are zero arguments.)
  2. [Marks: 2] Put the first argument (a file name) into a
     variable named filnam.
  3. [Marks: 7] If there is only one command line argument,
     prompt the user to enter the missing directory name and read
     the name from standard input.  Put the directory name
     (either the second command line argument or what the user
     entered from standard input) into the variable dirnam for
     use in the rest of the script.
  4. [Marks: 3] Display this exact sentence:
	You are processing file 'XXX' and directory 'YYY'.
     where XXX is the contents of the filnam variable and YYY is
     the contents of the dirnam variable containing the directory
     name that the user specified.  Use the exact punctuation.
  5. [Marks: 5] Verify that the path named by the dirnam variable
     is a directory; otherwise, exit with an error message.
     (i.e. Exit if the path is not a directory.)
  6. [Marks: 5] Verify that the path named by the dirnam variable
     is writable; otherwise, exit with an error message.  (i.e.
     Exit if the directory is not writable.)
  7. [Marks: 5] Verify that the path named by the dirnam variable
     is searchable; otherwise, exit with an error message.  (i.e.
     Exit if the directory is not searchable.)
  8. [Marks: 2] Put the file pathname $dirnam/$filnam into a
     variable named diffout. (Do not create this file yet.)
  9. [Marks: 5] Verify that the file named by the diffout
     variable is zero size or nonexistent; otherwise, exit with
     an error message.	(i.e. Exit if non-empty.)
  10.
     [Marks: 3] Make up a pathname for a temporary file and put
     it into a variable named tfile. Use the process ID of the
     current process in the pathname.  The pathname of the
     temporary file should be under the /usr/tmp directory.  (Do
     not create the file yet.)
  11.
     [Marks: 4] Sort the password file and place the output into
     the temporary file named by the tfile variable.  Exit with a
     non-zero exit status if the command fails.
  12.
     [Marks: 3] Generate the lines of difference between the
     contents of the password file and the contents of the
     temporary file and put the resulting output into the file
     named by the diffout variable.
  13.
     [Marks: 2] Save the exit status of the difference command in
     a variable named dstat.
  14.
     [Marks: 6] If the size of the file named by the diffout
     variable is greater than zero, append this exact message to
     the file named by the diffout variable:
	Difference exit status was XXX.
     where XXX is the contents of the dstat variable from a
     previous step.  Exit with a non-zero exit status if the
     appending command fails.