Command of the Hour

[Ian-144]

Ok, I want to start a bit of a discussion here - I want everyone to
chime in and tell the list of any random, obscure and useful commands
they know of. Anything you have come across that has helped you in
some way or you thought would be really handy in some situation,
doesn't matter what.


I'll start the ball rolling with several top variants:

atop - I just had an issue where gnome wasn't logging in, but seemed
to be stuck constantly accessing the hard drive. This command saved me
by showing me exactly which program was using the hard drive and a
quick aptitude remove mlocate later my system was working perfectly
again. It monitors CPU, memory, disk and network highlighting any that
are particularly stressed and shows the processes responsible.
Processes are only displayed if they have done something interesting
since the last update. Kernel patches can be taken to enhance the
experience if one is so inclined.

htop - Awesome ncurses graphical top. Looks pretty, coloured, and
simply highlighting a process and pressing 'S' will attach strace to
it to see what that run away process is actually up to. Tag multiple
processes and alter the niceness of them all at once or just kill em'
all. 'T' toggles between process tree view and ordinary top view.

powertop - I'm sure lots of people know about this one by now, but for
anyone who doesn't it can show you various information about what is
chewing up energy in your system and provide some recommendations for
conserving power.

iftop - top for network traffic. Shows the traffic going to and fro on
every individual transfer and totalled down the bottom in ncurses bar
graph style. Amounts are displayed for the last 2, 10 and 40 seconds.
Filters can be applied if one is only interested in a subset of the
total traffic, and it can naturally do hostname lookups and show port
numbers/service names.

ntop - another network top, but this one starts a web server on port
3000 to display it's results with pretty graphs. It has the advantage
that it provides much more detail - it breaks packets down by size,
protocol, etc. It has many displays to analyse the data in varying and
sometimes entertaining ways. Of course, being heavyweight as it is, if
all you need to know is that traffic is flowing from A to B, firing
this one up may be overkill, though it would easily suit as a very
quick and dirty network monitoring solution.


And a few others that I haven't found so useful myself, but someone else might:

itop - top for interrupts. I can imagine it would be useful for
checking if hardware is getting the computers attention when it should
be.

jnettop - this is another network top. I prefer iftop since it gives
me a graphical display (and it's help page is somewhat more detailed
than "I must write something here... :)").

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[Mike Carden]

On Tue, Sep 16, 2008 at 4:25 AM, Ian <darkstarsword@...> wrote:

> I'll start the ball rolling with several top variants:


Top stuff Ian.

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[Andrew Janke]

> Top stuff Ian.

<tick>

I realise that these ones may well be more well-known but here goes.

vidir - ever want to rename/remove a bunch of files in some directory
and got tired of typing mv/rm and just wish to just "edit" a
directory?

mmv - yet another renamer meaning you can do this:

   mmv '*.hdr' '#1.img'



a
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[Brett Worth-2]

One I use a lot is fmt.  If I'm editing text in vi I normally use "set wm=5" to get the
line wrapping at the 5th to last column.  After making changes though the formatting gets
out of whack.  I then use the "!" with a moving command to send a block of the file
through "fmt". e.g.

        {      -  Go to the blank line before a paragraph.
        !}fmt  -  Send the paragraph through fmt.

Or 3 paragraphs

        !3}fmt

Or for the entire document (which is probably not what you want):

        1G!Gfmt

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[steve jenkin-2]

Ian wrote on 16/9/08 4:25 AM:

>
> I'll start the ball rolling with several top variants:
>

Ian,

Thanks for a great question and more so, for introducing me to new tools
here.

Perhaps you or someone on list knows how to chase down a problem I once saw:

 - a process was spawning/forking processes as fast as the system
   could do it.
   On Solaris I didn't have a good tool to identify the problem or
   find the process quickly  :-(


What do I use everyday?

 - top, lsof, traceroute/tracepath, nmap, tcpdump
 - ssh & rsync + the shell :-)

regards
s

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[Owen-24]

On Tue, 16 Sep 2008 04:25:35 +1000
Ian <darkstarsword@...> wrote:

> Ok, I want to start a bit of a discussion here - I want everyone to
> chime in and tell the list of any random, obscure and useful commands
> they know of. Anything you have come across that has helped you in
> some way or you thought would be really handy in some situation,
> doesn't matter what.


For all the times you forget to use sudo first up

sudo !!

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[David Tulloh-2]

Owen wrote:

> On Tue, 16 Sep 2008 04:25:35 +1000
> Ian <darkstarsword@...> wrote:
>
>  
>> Ok, I want to start a bit of a discussion here - I want everyone to
>> chime in and tell the list of any random, obscure and useful commands
>> they know of. Anything you have come across that has helped you in
>> some way or you thought would be really handy in some situation,
>> doesn't matter what.
>>    
>
>
> For all the times you forget to use sudo first up
>
> sudo !!
>
>  

And sudo tee
Because `sudo echo foo > file` won't work when you don't have permission
to change file, the shell does the redirection.
`echo foo | sudo tee file` will work for you.


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> And sudo tee
> Because `sudo echo foo > file` won't work when you don't have
> permission to change file, the shell does the redirection.
> `echo foo | sudo tee file` will work for you.

I use dd for this:

echo 1 | sudo dd of=/proc/sys/net/ipv4/ip_forward

- which gives you the same semantics as bash redirection (ie, the output
isn't copied to stdout)

Cheers,


Jeremy


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[Michael Cohen-5]

And of course the absolute best program for remote admin - screen,
everyone must already be using it...
If you put this in /etc/screenrc or ~/.screenrc it even has tabs:

# Screen configuration

# Statusbar
hardstatus off
hardstatus alwayslastline
hardstatus string "%{.bW}%-w%{.rW}%n %t%{-}%+w %=%{..G} %H %{..Y} %d/%m %C%a"

# Scrolling in xterms
termcapinfo xterm|xterms|xs|rxvt ti@:te@

# Miscellaneous
startup_message off

Michael.

On Tue, Sep 16, 2008 at 11:06 AM, Jeremy Kerr <jk@...> wrote:

>
>> And sudo tee
>> Because `sudo echo foo > file` won't work when you don't have
>> permission to change file, the shell does the redirection.
>> `echo foo | sudo tee file` will work for you.
>
> I use dd for this:
>
> echo 1 | sudo dd of=/proc/sys/net/ipv4/ip_forward
>
> - which gives you the same semantics as bash redirection (ie, the output
> isn't copied to stdout)
>
> Cheers,
>
>
> Jeremy
>
>
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> And of course the absolute best program for remote admin - screen,
> everyone must already be using it...

and while we're at it:

 http://ozlabs.org/~jk/docs/screen-x.php

: using screen to share a console between two users - helpful for
collaboration, without having to start an entire vnc session.

Cheers,


Jeremy
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[Michael James]

On Tue, 16 Sep 2008 04:25:35 am Ian wrote:
> random, obscure and useful commands

lsof

# What mis-begotten spawn of the devil has bound my http port?
>  lsof -i:http

# The service is running but outside clients can't see it.
# What ports do I need to open in the firewall?
> lsof -i -u squeezecenter

# And I couldn't have come up with the last example without "man"
> man lsof
Lots of stuff about how to run lsof


# Which brings up my least favourite command, ever seen this?
"The  full  documentation  for ls is maintained as a Texinfo manual.
  If the info and ls programs are properly installed at your site,
 the  command

              info coreutils 'ls invocation'

 should give you access to the complete manual."

# So try it ...  8^(
> info ls
You will be plunged into an emaxian hell
 from which there are only 2 escapes:
   - A PhD in computing science
   - Closing the shell window

# Further study will reveal that all this pain
#   is a primitive* attempt to implement hyperlinks.
# The web provides a useful implementation so try:

        http://localhost/cgi-bin/info2html



# And I couldn't finish without mentioning the Command of the Century
> rsync

# And then there's the Command of the Next Century
> refloat  <path 1> <path2>

Which finds similar branches below the paths given,
 and is an antidote to one to many rsync commands.

my $.02

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[Peter Barker-2]

On Tue, 16 Sep 2008, Ian wrote:

> Ok, I want to start a bit of a discussion here - I want everyone to
> chime in and tell the list of any random, obscure and useful commands

I've thought for many years I should be working more logging into my
workflows.  I decided to spend the few minutes to actually do it a while
back.

----
pbarker@milligan:~$ log "Cleaned up log command a little"
200809161159 - Cleaned up log command a little
pbarker@milligan:~$ log "Added a single comment to log command"
200809161200 - Added a single comment to log command
pbarker@milligan:~$ tail -2 ~/notes/log
200809161159 - Cleaned up log command a little
200809161200 - Added a single comment to log command
pbarker@milligan:~$ log "Noted that the almond tree needs pruning" garden
Section 'garden' (file /nethome/pbarker/notes/logs/garden) does not exist
pbarker@milligan:~$ touch /nethome/pbarker/notes/logs/garden
pbarker@milligan:~$ log "Noted that the almond tree needs pruning" garden
200809161201 - Noted that the almond tree needs pruning
pbarker@milligan:~$ cat /nethome/pbarker/notes/logs/garden
200809161201 - Noted that the almond tree needs pruning
---

There must be several similar commands out there, but *finding* one is the
trick.  Writing one seemed easier (and, of course, the NIH syndrome).

begin-base64 644 log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====

Another gem I came across recently was "stress";  loads a machine's
disks/cpu/memory/IO.  I used it to load a machine so I could check its
power-consumption-under-load.

Yours,
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[Robert Edwards-3]

I usually use the 'mail' command to do the equivalent of what you are
doing with 'log':

bob@puddleduck:~$ mail bob@wherever -s Garden
Need to prune the almond tree
.
bob@puddleduck:~%

Does most of what I see 'log' doing, but I can do it from diverse
(Internet connected) systems and my mail reader is usually not too
bad at filing messages by sender/subject and searching through them.
Also, mail works not too badly for collaborative work as well
(apparently, some people even wrote a Unix-like kernel using internet
mail for collaboration... :-)

Cheers,

Bob Edwards.

Peter Barker wrote:

> On Tue, 16 Sep 2008, Ian wrote:
>
>> Ok, I want to start a bit of a discussion here - I want everyone to
>> chime in and tell the list of any random, obscure and useful commands
>
> I've thought for many years I should be working more logging into my
> workflows.  I decided to spend the few minutes to actually do it a while
> back.
>
> ----
> pbarker@milligan:~$ log "Cleaned up log command a little"
> 200809161159 - Cleaned up log command a little
> pbarker@milligan:~$ log "Added a single comment to log command"
> 200809161200 - Added a single comment to log command
> pbarker@milligan:~$ tail -2 ~/notes/log
> 200809161159 - Cleaned up log command a little
> 200809161200 - Added a single comment to log command
> pbarker@milligan:~$ log "Noted that the almond tree needs pruning" garden
> Section 'garden' (file /nethome/pbarker/notes/logs/garden) does not exist
> pbarker@milligan:~$ touch /nethome/pbarker/notes/logs/garden
> pbarker@milligan:~$ log "Noted that the almond tree needs pruning" garden
> 200809161201 - Noted that the almond tree needs pruning
> pbarker@milligan:~$ cat /nethome/pbarker/notes/logs/garden
> 200809161201 - Noted that the almond tree needs pruning
> ---
>
> There must be several similar commands out there, but *finding* one is
> the trick.  Writing one seemed easier (and, of course, the NIH syndrome).
>
> begin-base64 644 log
> IyEvYmluL3NoCgpCQVNFRElSPSQoL2Jpbi9scyAtZCB+cGJhcmtlci9ub3Rl
> cykKCmZ1bmN0aW9uIHVzYWdlKCkgewogICAgZWNobyAiVXNhZ2U6IGxvZyBj
> b21tZW50IFtzZWN0aW9uXSIKICAgIGV4aXQ7Cn0KCk1FU1NBR0U9JDEKU0VD
> VElPTj0kMgoKaWYgWyAteiAiJE1FU1NBR0UiIF07IHRoZW4KICB1c2FnZQpm
> aQoKTE9HRklMRT0iJEJBU0VESVIvbG9nIgppZiBbICEgLXogIiRTRUNUSU9O
> IiBdOyB0aGVuCiBMT0dGSUxFPSIkQkFTRURJUi9sb2dzLyRTRUNUSU9OIgog
> aWYgWyAhIC1lICIkTE9HRklMRSIgXTsgdGhlbgogICAgIGVjaG8gIlNlY3Rp
> b24gJyRTRUNUSU9OJyAoZmlsZSAkTE9HRklMRSkgZG9lcyBub3QgZXhpc3Qi
> CiAgICAgZXhpdDsKIGZpCmZpCgpEQVRFPWBkYXRlICcrJVklbSVkJUglTSdg
> ClNUUklORz0iJERBVEUgLSAkTUVTU0FHRSIKCmVjaG8gIiRTVFJJTkciCmVj
> aG8gJFNUUklORyA+PiRMT0dGSUxFCg==
> ====
>
> Another gem I came across recently was "stress";  loads a machine's
> disks/cpu/memory/IO.  I used it to load a machine so I could check its
> power-consumption-under-load.
>
> Yours,

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[Brett Worth-2]

2008/9/17 Robert Edwards <bob@...>:
>
> I usually use the 'mail' command to do the equivalent of what you are
> doing with 'log':
>
> bob@puddleduck:~$ mail bob@wherever -s Garden
> Need to prune the almond tree
> .
> bob@puddleduck:~%

Bob,

Does the mail command cause your shell to switch from bash to csh?
That's weird!!  :-)

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[Robert Edwards-3]

Brett Worth wrote:

> 2008/9/17 Robert Edwards <bob@...>:
>> I usually use the 'mail' command to do the equivalent of what you are
>> doing with 'log':
>>
>> bob@puddleduck:~$ mail bob@wherever -s Garden
>> Need to prune the almond tree
>> .
>> bob@puddleduck:~%
>
> Bob,
>
> Does the mail command cause your shell to switch from bash to csh?
> That's weird!!  :-)
>

OK, you got me. A bit of careless cut and pasting which I fixed by hand.
Should have gone back and re-selected the text. Boy - you are
eagle-eyed!

Cheers,

Bob Edwards.
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[steve jenkin-2]

Robert Edwards wrote on 17/9/08 9:48 AM:

I'd like to propose Brett for the Inaugural "CLUG Eagle-Eye" award.
This had me chuckling this morning - really good fun!
[And isn't that a big chunk of our shared ethos?]

It really was quite spectacular - spotting the detail, with such speed.

The usual questions about 'awards':

 - how often?
 - who decides (being an anarchic collective, 'everyone'?)
 - what trophy?
 - special event, normal meeting, or just on-line?

Anyone got ideas for other *fun* awards??

 - best flame-bait
 - worst dressed geek
 - most pizza consumed in a sitting
 - best code or program [with a special category for Tridge  :-)]
 - longest thread
 - cutest toy or gizmo
 - Michael Still award for longest trip to a meeting
 - best and fairest website
 - ?????

> Brett Worth wrote:
>> 2008/9/17 Robert Edwards <bob@...>:
>>> I usually use the 'mail' command to do the equivalent of what you are
>>> doing with 'log':
>>>
>>> bob@puddleduck:~$ mail bob@wherever -s Garden
>>> Need to prune the almond tree
>>> .
>>> bob@puddleduck:~%
>>
>> Bob,
>>
>> Does the mail command cause your shell to switch from bash to csh?
>> That's weird!!  :-)
>>
>
> OK, you got me. A bit of careless cut and pasting which I fixed by hand.
> Should have gone back and re-selected the text. Boy - you are
> eagle-eyed!
>
> Cheers,
>
> Bob Edwards.

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[Robert Edwards-3]

I reckon Brett should get an extra slice of Pizza at the next
CLUG meeting, in recognition of this outstanding achievement!

And whoever wins "most pizza consumed in a sitting" can also
get an extra slice - at the same sitting!

Bob Edwards.

steve jenkin wrote:

> Robert Edwards wrote on 17/9/08 9:48 AM:
>
> I'd like to propose Brett for the Inaugural "CLUG Eagle-Eye" award.
> This had me chuckling this morning - really good fun!
> [And isn't that a big chunk of our shared ethos?]
>
> It really was quite spectacular - spotting the detail, with such speed.
>
> The usual questions about 'awards':
>
>  - how often?
>  - who decides (being an anarchic collective, 'everyone'?)
>  - what trophy?
>  - special event, normal meeting, or just on-line?
>
> Anyone got ideas for other *fun* awards??
>
>  - best flame-bait
>  - worst dressed geek
>  - most pizza consumed in a sitting
>  - best code or program [with a special category for Tridge  :-)]
>  - longest thread
>  - cutest toy or gizmo
>  - Michael Still award for longest trip to a meeting
>  - best and fairest website
>  - ?????
>
>> Brett Worth wrote:
>>> 2008/9/17 Robert Edwards <bob@...>:
>>>> I usually use the 'mail' command to do the equivalent of what you are
>>>> doing with 'log':
>>>>
>>>> bob@puddleduck:~$ mail bob@wherever -s Garden
>>>> Need to prune the almond tree
>>>> .
>>>> bob@puddleduck:~%
>>> Bob,
>>>
>>> Does the mail command cause your shell to switch from bash to csh?
>>> That's weird!!  :-)
>>>
>> OK, you got me. A bit of careless cut and pasting which I fixed by hand.
>> Should have gone back and re-selected the text. Boy - you are
>> eagle-eyed!
>>
>> Cheers,
>>
>> Bob Edwards.
>
>

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[Nathan Rickerby-2]

On Tue, Sep 16, 2008 at 08:10:18AM +1000, Brett Worth wrote:
> One I use a lot is fmt.  If I'm editing text in vi I normally use "set wm=5" to get the
> line wrapping at the 5th to last column.  After making changes though the formatting gets
> out of whack.  I then use the "!" with a moving command to send a block of the file
> through "fmt". e.g.
>
> {      -  Go to the blank line before a paragraph.
> !}fmt  -  Send the paragraph through fmt.

Something similar that also works quite well is par
http://www.nicemice.net/par/ it handles multiple levels of quoting
characters which is really handy for email.

One vi command I like is !!sh to execute the current line in a shell.
It's useful if you're building up a long one-liner and want to easily
document the output and your progress.  Or if you want to include the
output of previous commands in future commands, for example

ls *txt<esc>!!sh
  edit the output, insert cat at the front of the line and | grep whatever at
  the end of the line, then
<esc>!!sh

I find it easier to use than :r!

also !!dc for a calculator, for example
4534 445 * 5 / 2 + p<esc>!!dc
and again you can use the output of that in your next calculation.
It probably doesn't need need pointing out, but if you yyp before you
!!dc you can keep a copy of the input.

On Tue, Sep 16, 2008 at 11:06:11AM +1000, Jeremy Kerr wrote:

> > And sudo tee
> > Because `sudo echo foo > file` won't work when you don't have
> > permission to change file, the shell does the redirection.
> > `echo foo | sudo tee file` will work for you.
>
> I use dd for this:
>
> echo 1 | sudo dd of=/proc/sys/net/ipv4/ip_forward
>
> - which gives you the same semantics as bash redirection (ie, the output
> isn't copied to stdout)

As much as I appreciate that use of dd, tee has the advantage that you
can use the -a option to append to the file like >>.
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