Extracting 3word lines from files

[NeoStarO1]

HI Everyone,

I am plumb stumped on this one.
What I need to be doing is to extract all the words that have only 3 letters to the word per line. So only lines that have 3 characters per line.

I have read teh tutorial here at linuxjunior and plus my two textbooks plus my two personal unix books that i have bought and after the full day of banging my head with grep and such I am no where futher than where i started this morning.

So just so you have idea what Im talking about.
Say my file consist of these words.

Linux
Unix
Redhat
Cat
rabbit
dog
Konquerer
KDE
Flux

The only output i want to see are the words.
Cat
dog
KDE

I can't seem to accomplish this at all from the CL.

TIA

Edit: One other question, I often see this result when doing commands, I will type command hit enter and it will return with this...
MORE:>
What does that mean? I can't find any reference on this.

[GnuVince]

Here's a small Python script that should do the trick:

import sys

try:
  f = open(sys.argv[1])
  lines = f.readlines()
  for line in lines:
    if len(line) == 4:  # We also count newlines (\n)
      print line
except Exception, e:
  print "Uncaught exception:", e

[NeoStarO1]

Yes I know a script would be easier, however we are not allowed to use a script for this particular question. It has to be done from the command line. :-\

[t048]

Did you try the suggestion I gave @ techimo?

[GnuVince]

[vince@vincent: ~/prog/python]% grep '^[a-zA-Z][a-zA-Z][a-zA-Z]$' heh 
KDE
Vim
Bar
Foo

[NeoStarO1]

Type in this
grep '^[a-zA-Z][a-zA-Z][a-zA-Z]$' /home/pathfilename
and got cannot open file.

[quote author=GnuVince link=board=10;threadid=4337;start=0#43222 date=1027708856]

[vince@vincent: ~/prog/python]% grep '^[a-zA-Z][a-zA-Z][a-zA-Z]$' heh 
KDE
Vim
Bar
Foo

[/quote]

[NeoStarO1]

[quote author=t048 link=board=10;threadid=4337;start=0#43220 date=1027708256]
Did you try the suggestion I gave @ techimo?
[/quote]

Yes I did, same response. ???

[NeoStarO1]

grep '^[a-zA-Z][a-zA-Z][a-zA-Z]$' pathfilename

Killer dude!!! I couldn't get the thing to work, so it keep saying cannot open file im like what the hey, i can open the file doinga cat. well apparently or something cat is not as case sentitive or something, dunno. ???

Anyhow i decided to do a ls -a of the direcotry the file is in and whoa dude, i added 4 charachters too much to the end of the words file.
its jut plain ole words nothing else.
i was putting in words.dat

Im a happy camper now Thanks guys! You're great!!!!!!

[NeoStarO1]

hmmm okay, what if a file had words like this in it.

u.s

why doesn't the same command as posted above include these?


EDIT:
Okay got it, had to do with a few pipes. Ended up doing this...
grep '^U[a-zA-Z|.][a-zA-Z|.]$' | grep '^[a-zA-Z][a-zA-Z][a-zA-Z]$'

[cloverm]

[quote author=NeoStarO1 link=board=10;threadid=4337;start=#43231 date=1027710968]
hmmm okay, what if a file had words like this in it.

u.s

why doesn't the same command as posted above include these?
[/quote]

Try it like this. Looks cleaner anyway:

grep '^...$' path/filename