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Basic Command line in unix

 

Basic Command line in unix
machaoxxx

23 Sep, 2009 - 12:04 PM
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i just started learning about unix and such, and i'm trying out these problem i found online. Just tell me if i'm getting this. Currently downloading Untubun to run unix os on my comp.

problem: find all logged-in users with usernames of at least four characters.
$ who | cut -c1-8 | [a-zA-Z]\{4,\}$

so what should display if i use who is:
[Person name] [sum stuff] [date] [time]
ex:
Tomf Xyz23 23/23/23 23:23
Tam Xyz23 23/23/23 23:32
lomg Xyz23 23/23/23 23:32
jay Xyz23 23/23/23 23:32

a.) who display above
b.) using cut , i should i extract the first 1 to 8th character
c.) then match any alphabetical character that at least 4 character long
d.) and the $ mean to do for each line

This post has been edited by machaoxxx: 23 Sep, 2009 - 12:09 PM

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moopet

RE: Basic Command Line In Unix

23 Sep, 2009 - 01:17 PM
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QUOTE(machaoxxx @ 23 Sep, 2009 - 07:04 PM) *

$ who | cut -c1-8 | [a-zA-Z]\{4,\}$
a.) who display above
b.) using cut , i should i extract the first 1 to 8th character
c.) then match any alphabetical character that at least 4 character long
d.) and the $ mean to do for each line


Well, your cut is probably ok, depends on what your version of who I guess.

As far as your matching goes, you can't just shove a regular expression on the end of the line, you need to use a command to search on it. Your winner here is grep:
CODE

who | cut -c1-8 | grep '[a-zA-Z]\{4\}'


Note that this will only match all lines with 4 or more consecutive alphabetic characters. who can, depending on the configuration, return lines with text in which would match this besides the username...
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NoobKnight

RE: Basic Command Line In Unix

25 Sep, 2009 - 01:38 PM
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This works: who -u | awk '{print $1}' | grep "....."

Here is a live example


xxxxxx: who -u
matthewm ttyp1 Sep 25 07:37 8:50 2807
montem ttyp2 Sep 25 08:10 . 4716
chuckp ttyp4 Sep 25 08:25 2:12 6244
chuckp ttyp5 Sep 25 08:26 8:01 6346
danl ttyp6 Sep 25 08:28 6:32 6487
danl ttyp7 Sep 25 08:29 2:31 6563
timn ttyp8 Sep 25 08:57 6:43 8760
danl ttyp10 Sep 25 09:19 0:06 10492
danl ttyp11 Sep 25 09:20 0:07 10745
danl ttyp12 Sep 25 11:23 3:12 11031
johng ttyp13 Sep 25 10:01 5:36 407
danl ttyp14 Sep 25 11:25 2:56 11195
billc ttyp15 Sep 25 14:25 2:02 21060
tracyt ttyp16 Sep 25 15:00 0:06 22814
montem ttyp24 Jun 4 11:05 old 10953


Notice it doesn't select the people with only 4 chars in their logname.
xxxxxx: who -u | awk '{print $1}' | grep "....."
matthewm
montem
chuckp
chuckp
johng
billc
tracyt
montem
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