[Wolves] Hello...

[Octavio Augusto Sánchez Velázquez]

El lun, 15-06-2009 a las 10:40 +0100, Adam Sweet escribió:
> Octavio Augusto Sánchez Velázquez wrote:
> > Hello, I'm new to this mailing list, currently I don't live in
> > Wolverhampton but I will upon September.
> 
> Welcome to the LUG :) Are you a Spanish student coming to Wolverhampton
> University? I went there myself and was friends with a lot of Spanish
> students, it was maybe 7 or 8 years ago now so they have all long since
> left. Where are you from?

I am from Mexico, not from Spain, but yes I'm going to study to
Wolverhampton University.

> > I'm just getting used to the CLI and I think that is better than
> > GUI, but is harder to learn. Specially all does languages like sed, and
> > awk which I can't understand.
> 
> It took me quite a long time to get used to the command line, I started
> slowly but picked up speed once I understood a few commands and got the
> basics of how things go together using pipes '|' and redirects '<' or '>'.
> 
> I'm no master of sed or awk but the simple things aren't too hard and
> you can build up from there, they're just difficult to pick when you
> don't have a real reason to use them.
> 
> For example, use awk to pull a field out of of some output, such as
> finding the process IDs from the output of ps, especially useful when
> using grep to find processes owned by a particular program or service:
> 
> adams at selenium:~$ ps ax | grep apache
>  3933 ?        Ss     0:02 /usr/sbin/apache2 -k start
> 11133 ?        S      0:00 /usr/sbin/apache2 -k start
> 11135 ?        S      0:00 /usr/sbin/apache2 -k start
> 11136 ?        S      0:00 /usr/sbin/apache2 -k start
> 11138 ?        S      0:00 /usr/sbin/apache2 -k start
> 11139 ?        S      0:00 /usr/sbin/apache2 -k start
> 25712 pts/0    S+     0:00 grep apache
> 
> You can see there is a process running called 'grep apache', which is
> the grep finding its own process looking for apache. You can exclude
> things from grep with -v so you can stop grep finding itself with 'grep
> -v grep':
> 
> adams at selenium:~$ ps ax | grep apache | grep -v grep
>  3933 ?        Ss     0:02 /usr/sbin/apache2 -k start
> 11133 ?        S      0:00 /usr/sbin/apache2 -k start
> 11135 ?        S      0:00 /usr/sbin/apache2 -k start
> 11136 ?        S      0:00 /usr/sbin/apache2 -k start
> 11138 ?        S      0:00 /usr/sbin/apache2 -k start
> 11139 ?        S      0:00 /usr/sbin/apache2 -k start
> 
> Now awk out the first field which contains the process IDs:
> 
> adams at selenium:~$ ps ax | grep apache | grep -v grep | awk {'print $1'}
> 3933
> 11133
> 11135
> 11136
> 11138
> 11139
> 
> Awk uses tabs as field separators, so I'm telling it to pull out the
> first one.
> 
> Sed means stream editor. You take a stream of data, normally output from
> a command or a from file and you edit it on the fly. You can't edit a
> file in place with sed as it will still be reading in the file as you're
> trying to write it. When editing files you have to write the output to
> another file and then move it over the original afterwards.
> 
> As a fairly useless example, I'll take the output from the above awk
> command and change all the 1s to 2s:
> 
> ps ax | grep apache | grep -v grep | awk {'print $1'} | sed 's/1/2/g'
> 3933
> 22233
> 22235
> 22236
> 22238
> 22239
> 
> Here I am passing in the output from the previous commands using the
> pipe and telling sed to substitute (the s) 1 for 2 globally (the g). You
> see how these commands build up? You just have to get data from A to B
> to C, modifying it on the way. The difficulty is in knowing the commands
> to do what you need in the first place :) Realistically, most normal
> people won't ever need sed and awk :)
> 
> > Any way, I am willing to read all mail discussion over here so I can
> > learn more and get some ideas about everything here.
> 
> Welcome aboard. If you're interested and you can make it to some of our
> meetings when you arrive, I'm sure one of us can do a beginners guide to
> the command line presentation, I've been meaning to do one for years but
> most of the people it would have been useful to didn't come to meetings.
> 
> Regards,
> 
> Adam
Yes, I get know that sed s///g changes the strings of the first // for
the second //, this get's me another doubt, what about tr??? awk, I
really don't get it I usually copy and paste it and that's all. In your
example I didn't get what you were doing because I didn't know what ps
was (nothing that man ps couldn't solve), I usually use top insted, but
from now on I will use this ps sweet, hehe
thank you.