String editing using sed? awk? Post: 302370547

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Homework and Emergencies Homework & Coursework Questions String editing using sed? awk? Post 302370547 by bakunin on Wednesday 11th of November 2009 07:52:42 PM

11-11-2009

Registered User

Ok, this is about the script i expected. It has several problems, but first, lets analyze your problem correctly. Software engineering (and script programming is a form of software engineering) is about correctly analyzing the problem before you envision a solution.

Your "find" command compares dates - the date/time the file local.cshrc has been changed to when the file index.html in the users home directory. If a new user is created after the last change of the skeleton file his file ~/index.html will be newer regardless of being changed or not. On the other hand if the skeleton file is changed even the files reported as changed before will be reported as not changed. So you don't find the correct files in first place.

Lets see: when a new user is created s/he is delivered some standard version of index.html. If s/he changes it it will differ from this standard file, if not then not. Now this is indeed a criterion which will pick out the right files, yes?

So, your task is to find a unix utility which compares two files and finds out if they differ or not. If there is such an utility we could write the following program (in pseudocode):

Code:

while (cycle through all users)
     do
     if (~thisusers/index.html is equal  to the standard index.html)
          do nothing
     else
          write a corresponding line to your output file
     endif
enddo

There are two things you can do for now:

1) find a way to get all the users names. (You will need this to set up the while-loop above.) I could tell you, but i don't want to spoil your fun finding it out.

2) find a unix command which compares two files and finds out if they are equal (you will need this for deciding the if-construction).

Report back here with your answers and i will give you the directions for the next stage.

Sorry for dragging this out this way, but i cannot give you enough directions at once without giving away the solution. As the spirit of this board is to help you learn and not spoon-feed you solutions we have to do it this way. As i am convinced you will soon find out Unix is not only a lot of fun to work with but also a lot of fun to learn about, so enjoy it while the learning experience lasts.

bakunin

bakunin

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LEARN ABOUT ULTRIX

indxbib

lookbib(1)						      General Commands Manual							lookbib(1)

Name
       indxbib, lookbib - build inverted index for a bibliography, lookup bibliographic references

Syntax
       indxbib database...
       lookbib database

Description
       The  makes  an inverted index to the named databases (or files) for use by and These files contain bibliographic references (or other kinds
       of information) separated by blank lines.

       A bibliographic reference is a set of lines, constituting fields of bibliographic information.  Each field starts on a line beginning  with
       a  ``%'',  followed  by	a key-letter, then a blank, and finally the contents of the field, which may continue until the next line starting
       with ``%''.

       The command is a shell script that calls and The first program, truncates words to 6 characters, and maps upper case  to  lower	case.	It
       also  discards words shorter than 3 characters, words among the 100 most common English words, and numbers (dates) < 1900 or > 2000.  These
       parameters can be changed.  The second program, inv, creates an entry file (.ia), a posting file (.ib), and a tag file (.ic),  all  in  the
       working directory.

       The command uses an inverted index made by to find sets of bibliographic references.  It reads keywords typed after the ``>'' prompt on the
       terminal, and retrieves records containing all these keywords.  If nothing matches, nothing is returned except another ``>'' prompt.

       It is possible to search multiple databases, as long as they have a common index made by In that case, only the first argument given to	is
       specified to

       If  does  not  find the index files (the .i[abc] files), it looks for a reference file with the same name as the argument, without the suf-
       fixes.  It creates a file with a '.ig' suffix, suitable for use with It then uses this fgrep file to find references.  This method is  sim-
       pler to use, but the .ig file is slower to use than the .i[abc] files, and does not allow the use of multiple reference files.

Files
       x.ia, x.ib, x.ic, where x is the first argument, or if these are not present, then x.ig, x

See Also
       addbib(1), lookbib(1), refer(1), roffbib(1), sortbib(1),

																	lookbib(1)