Test #2 Shell Programming

Shell Programming - Points: 88  (13 of 25%)

Write code for an executable shell script that will do the following
actions, in the exact order given below.  (You will write approximately 50
lines of executable code, plus a step number comment before each step.)

Summary and Purpose:
     The first argument to the script should be a URL of a Unix tar file.
     The second argument is an optional program name.  (The script will
     prompt the user for a missing second argument.)  The script will
     fetch the URL and look for the program name in the tar file.

Only Step Comments are Required:
     Put only a one-line comment containing the step number in front of
     the executable code in each step.
                   ________________________________________

  1.   [Points: 6] Start your script with a standard NET2003 script
       header; but, do not include the Purpose or Assignment Label.
       (Remember the One-Line Description and Syntax.)

  2.   [Points: 9] If the number of arguments is incorrect, issue a good
       error message (follow the NET2003 guidelines) and exit the script
       with status 1.

  3.   [Points: 1] Put the first argument (the URL) into a variable named
       url.

  4.   [Points: 12] If the string in variable url begins with the seven
       characters http://, display Fetching UUU from web..., where UUU is
       the user's URL; otherwise, issue a good error message and exit the
       script with status 2.

  5.   [Points: 2] Put a unique temporary file name (located in the
       standard Unix temporary file directory) into a variable named tmp.
       The file name must contain the current process ID number.

  6.   [Points: 10] Fetch the raw (unformatted) URL contained in the url
       variable into the file named by the tmp variable.  If the fetching
       fails with a bad return status, issue a good error message, remove
       the file, and exit the script with status 3.

  7.   [Points: 9] Make sure the fetched URL file is not empty (has a file
       size larger than zero); otherwise, issue a good error message,
       remove the file, and exit the script with status 4.

  8.   [Points: 3] Remove all write permissions from the the file
       containing the fetched URL.  Do not change any other permissions.
       Quick-exit the script (no message) with status 5 if changing
       permissions fails.

  9.   [Points: 10] Run the file command on the fetched URL file and look
       for the string 'tar archive'. If the fetched URL file is a tar
       archive (the string is found), display Looking in tar archive...;
       otherwise, issue a good error message and exit the script with
       status 6.

  10.  [Points: 7] If there are two arguments, put the second argument
       (the program name) into a variable named prog; otherwise, get the
       missing program name from the user and put it into variable prog.
       Quick-exit the script (no message) with status 7 if the user
       signals EOF to the script.

  11.  [Points: 10] Produce a table of contents (TofC) of the tar archive
       file and look in the TofC for the program name string contained in
       the prog variable.  If the string is found in the tar archive TofC,
       display Program PPP is contained in UUU, where PPP is the program
       name found and UUU is the URL of the tar archive; otherwise, issue
       a good error message and exit the script with status 8.

  12.  [Points: 7] If the parent directory is writable and a file named
       foo.tar exists in the current directory, move the file to the
       parent directory.  Quick-exit the script (no message) with status 9
       on move failure.

  13.  [Points: 2] Rename the tar archive file to be foo.tar. Quick-exit
       the script (no message) with status 10 if the rename fails.

Put a one-line comment containing the step number in front of the
executable code in each step.