Due Thursday, 12 October 2017, 11:59 PM.

The easiest way to create and edit these is to put them in a text file. You can then source this file to declare or redefine the aliases in the current login shell. If you named the file aliasAssn, you can initialize them with the command sequence :

. aliasAssn

The source command will read each line of the file and enter it into the command line buffer as if you were typing it in yourself. Because you are sourcing the command sequence, DON'T put in the shebang (#!/bin/bash). But, do put in comment lines. These will be ignored by the command interpreter.

The aliases will now be loaded into your current login shell. Test your aliases. If you find mistakes, simply edit your aliasAssn file, fix your mistakes, save, and source the file again.

To prepare for this assignment, do the following.

Create a directory under your home directory called Backup.

Read the lectures on the command line and delimiters, variables, and aliases.

Read the man pages on the following entries :

test command.
find command.
date command.

Give the problem number, a general description ( you don't have to copy the problem verbatim ) and any comments to help yourself.

To figure out what comments to use, pretend that you were going to be a TA next year for this course and that you were going to use your assignment as a key to counsel any students asking for help. How would you describe your answers so you could understand it after a year.

When creating an alias, if possible, use the environmental variables instead of specific values to make the alias portable.

For example, if you need to access your home directory, use the variable $HOME instead of /home/hopper/z######. This will allow your T.A. to test your functions in her/his account.

Be careful to notice whether the alias has caps in its name.

Write the following aliases :

Choose formatting options that generates a single string of digits( numbers ) with no white-space but with all digits, so a 4 digit year, a 3 digit day of the year, hours as 2 digits in 24 hour units, and minutes and seconds in the range 00-59.

The purpose of this is to generate a string that can be used by another alias to timestamp a backup copy of a file by adding a filename extension.

• Prompts the user for a filename
• Uses read to assign the user's input into a variable that uses your login ID as it's name. Hard code your Z-ID as the variable name.
  read z912730

• Calls getname# remember it stores it in a variable named your zid.
• Tests to see if filename given is regular file, if not :
  print error "Not a regular file"
  Set return code to 1
• If first test successful, tests that the file is readable, if not
  print error "Can't read"
  Set return code to 2.
• If error, only one error should run. You may have to use parentheses within parentheses.
• You may have to do multiple open and closed quotes to get the can't to print correctly.

  # Consider the following :
  # assign the string "It's translated" including double quotes to a variable.
  var='"It'\''s translated"'
  echo $var
  "It's translated"
  
  # If you match carefully, you'll see that the 1st set of single quotes is
  closed before the backslash quotes a lone single quote and then a second pair
  of single quotes encloses the rest of the string.
  

if you do an exit # inside parentheses, (exit 2), the exit exits the parentheses and sets the return status without exiting the current login shell.

You can break this down into 3 aliases. 1st alias does the file exit test, the second does the read test, and the 3rd (vfile) combines them. This will make it easier to test.

You may also have to embed parentheses inside paretheses to get the proper logic. You may need to use \ or close and open different quotes to quote the ' in can't

The alias should do the following :

• Calls vfile to get a valid file.
• Copies named file to Backup but only after testing success of vfile.
• Use copy with -i to check for overwrite of another backup before proceeding.

The Backup alias should do the following :

• Use vfile to get the file to be backed up.
• Copies the file to Backup using cp -i.
• But append a timestamp as an extension on to the name in the Backup directory.
  • Use sed to remove any path info from the user specified filename. You may store this "cleaned" file name in a new variable or you may use the graves to generate the new name in the copy command sequence.

    #Try the following :
    
    fn="/var/www/file1"
    echo $fn|sed "s#^.*/##"
    nfn=`echo $fn|sed "s#^.*/##"`
    echo $nfn
    #sed removes all characters up to and including the last /
    

    Sugestion : write an alias called trim that just trims the path off of the specified filename. trim can then be invoked in cp command sequence.

The alias should do the following :

• Prompt the user for the directory to start search in.
• Prompt the user for the filename to search for.

• Redirect any error messages to /dev/null