The ECN No Name Newsletter is no longer being published. This is an archived issue.

Using EX And VI Commands

Stacey Clark

There are special characters you can use in VI and EX:

      $     =  end of line
      ^     =  beginning of line
      .     =  match any one character
      *     =  repeat (r* could be r, rr, rrrrr, etc.)
      .*    =  everything on the line
      a.*z  =  everything from the first a on a line
               to the last z on a line

Suppose you just got all new Sun accounts, and you wanted to create a .rhosts file to transfer files easily back and forth between machines without having to type in your password.

The first step is to log in to a Sun and determine what machines are on the local network. To accomplish this type the ruptime command and redirect the output into your .rhosts file with "ruptime > .rhosts". Then use the EX or VI editor to remove unwanted hosts and modify the file. Remember the ruptime output will depend upon where you are when you type the command. Your output might look like:

     argon;up 20+18:34,;0 users,;load 0.02, 0.00, 0.00
     atoms;up 25+03:16,;1 user,;load 0.97, 1.70, 1.72
     berkelium;up 141+17:48,;0 users,;load 0.52, 0.30, 0.02
     bromine;up 20+00:53,;4 users,;load 0.21, 0.36, 0.09
     chlorine;up 26+01:33,;5 users,;load 0.44, 0.30, 0.03
     cn;up 44+07:40,;23 users,;load 3.72, 3.68, 3.65
      ... etc.

Now you want to convert the information gathered (machine names plus all the other stuff) into something that looks like:

                  argon.ecn.purdue.edu  stacey

except with your login instead of "stacey".

Achieving this deletion/replacement procedure can be a single or multiple step process depending on how you elect to use the special matching characters presented earlier.

Two Step Method

First erase everything to the right of the machine name (which is everything after the first space) by typing ":1,$s/ .*//". This will produce:

           argon
           atoms
           berkelium
           bromine
           chlorine
           cn

              ...etc.

There are many ways to specify "all lines."

 Referencing the exact number of lines in a file:   1,20  for
     lines 1, 2, 3,...,20.

 1,$ because $ in the line  number  part  of  the  substitute
     command means "last line of file."

 You could use "%", which is shorthand for "all lines."
 

Use the method that is easiest for you to remember.

Next, add your desired text to the end of each line.   Using  the
dollar  sign twice in the substitute command, I am telling VI and
EX to perform the asked for substitution to  all  lines   ":1,$s"
(from  the  first  line (1) through the last line of the file ($)
substitute (s)) and then to append to the end of the  line  "/$/"
the text string ".ecn.purdue.edu  stacey".

The complete command reads
":1,$s/$/.ecn.purdue.edu    stacey/"
and produces:
        argon.ecn.purdue.edu stacey
        atoms.ecn.purdue.edu stacey
        berkelium.ecn.purdue.edu stacey
        bromine.ecn.purdue.edu stacey
        chlorine.ecn.purdue.edu stacey
        cn.ecn.purdue.edu stacey

One Step Method

To made the changes with one command, type:
":%s/  .*/.ecn.purdue.edu  stacey/"


Remember the substitute command is basically:

starting line number, ending line number substitute / old / new /
                       :1,55 s /dog/bird/




webmaster@ecn.purdue.edu
Last modified: Friday, 12-Sep-97 19:15:29 EST




HTML