Javier López's questions

I'm working on a custom Debian package and I'd like to delay its installation/configuration when installed with other packages, eg;

$ sudo apt-get install htop curl my-pkg rsync ...

Apt-get should install all other packages and let my-pkg to the end, any ideas to accomplish this within the maintainer scripts?

I'm working in some Debian packages and at some point I'd like to add optional dependencies, e.g. if foo-pkg is marked as to be installed at the same time as my-pkg let foo-pkg install first and then continue with my-pkg, if foo-pkg is not available or not marked to be installed just continue.

I could use the Recommend: field but as far as my tests has gone it doesn't force apt-get to install foo-pkg first, also, I don't have control over foo-pkg, any ideas?

I'm looking for a way to do quick calculations in the terminal (using utilities available in Ubuntu minimal) and get accurate fail errors when the math syntax is incorrect, eg: cli-calculator "foo+bar" || echo invalid math syntax

Some of the inputs would be:

• 1+1 #should print 2 and return a 0 code

• 5/2 #should print 2.5 and return a 0 code

• 1/0 #should return a non 0 code

• foo+bar #should return a non 0 code

I've tried bc, shell integrated arithmetic, expr, awk, perl and python but so far none has satisfied fully my requirements, so I'm looking for alternatives, follow use cases:

• bc, it's able to do operations with float numbers but doesn't return error codes on invalid syntax input

  $ echo "1/0" | bc -l && echo all is fine || echo math syntax error
  Runtime error (func=(main), adr=3): Divide by zero
  all is fine
  $ echo "foo+bar" | bc -l && echo all is fine || echo math syntax error
  0 #should return an error
  all is fine
  

• Shell integrated arithmetic and expr, don't support operations with float numbers and return valid codes on invalid math input

  $ echo $((5/2))
  2 #should return 2.5
  $ echo $((foo+bar))
  0 #should return an error
  $ expr 5 / 2
  2 #should return 2.5
  $ expr foo+bar
  foo+bar #should return an error
  

• awk|perl, don't return invalid status codes on invalid math input.

  $ awk "BEGIN {print foo+bar; exit}"
  0 #should return a non 0 number and probably output an error
  $ echo "foo+bar" | perl -ple '$_=eval'
  0 #should return a non 0 number and probably output an error
  

• python, supports float arithmetic operations and return status errors on invalid math syntax but it's slow.

  $ python -c 'from __future__ import division; from math import *; print(foo+bar)' && echo all fine || echo math syntax error
  NameError: name 'foo' is not defined
  math syntax error #good!
  $ python -c 'from __future__ import division; from math import *; print(5/2)' && echo all fine || echo math syntax error
  2.5` #good!
  all fine
  

Any ideas?

I commonly install/remove a bunch of software after installing Ubuntu, I wonder about the methods to automate it.

Is anything like /etc/apt/packages where I could define which packages I want?

Pressed configuration files work on initial setup, however I'd like it to work regardless of the status of the system.

I have this 862MB base.tgz image which is taking a considerable amount of time to decompress on every pbuilder invocation, I've read that there exist a cow alternative who keeps the files uncompressed so I'm willing to start using it, unfortunately I don't remember exactly the steps to recreate this image, so I'd prefer to convert it instead of starting from scratch. Is there any method to do so?

I'm willing to create a cron job for a package but when I define it in debian/cron.d it gets installed as /etc/cron.d/package. I'd prefer to be able to change the name of the cron job to be something like /etc/cron.d/foobar.

I'm just being curious about how or from what package the /etc/inputrc file is generated in an Ubuntu system. I've tried:

$ apt-file search /etc/inputrc

But it outputs nothing. No package assigned?

I've seen there exist a inputrc file in the libreadline6 and bash packages but neither of them seems to be responsible of it (unless I failed to see the steps who produce it in one of those packages).

I'm interesting in avoiding the installation of the content of a debian package when a file is present in the system, eg. /usr/local/bin/token.

I'd like than the debian package will look for the token in the pre-installation phase (preinst?) and decide to install or not the content afterwards, maybe I could just delete the content to avoid copying anything.

Whenever I use mpc next or any other player (ncmpcpp) MPD will play the next song and will remove the previous song from the playlist (generated by mpc add /).

My mpd.conf is located at /etc/mpd.conf

And I've not found any directives associated to this annoying behavior. I'd prefer that MPD jump to the next song but without removing any previous songs.

Any help is welcome.

I have the following script:

#!/bin/sh

[ "${#}" -eq "0" ] && (printf "%s\\n" "${0}: word ..." >&2; exit 1)

_whats()
{
    [ -z "${1}" ] && return 1
    [ -z "${2}" ] && more_than_one="1"

    for word; do
        response="$(dig +short txt ${word}.wp.dg.cx)"
        printf "%s\\n" "${response}"
        if [ -z "${more_than_one}" ]; then
            printf "\\n%s\\n\\n" ":::::::::::::::::::::::::::::::::::::::::"
        fi
    done
}

_whats "${@}"

It works great when I call it this way:

whats shell\ script dns #it ouputs two definitions (shell script and dns)

However I'd also to call it this way:

echo shell\ script dns | whats

I'm just used to it, all other unix commands can do it, how would you implement it in a shell script?

Is possible to have a ~/.juju/environments.yaml file like this?:

environments:
  sample:
    type: ec2
    access-key: $(cat access-key)
    secret-key: $(cat secret-key)
    control-bucket: juju-8b53699f85c0438c96897ce75f633aa1
    admin-secret: 9a7c512f938f4bafb96365d7ceaf569b
    default-series: precise
    ssl-hostname-verification: true

I'd like to get those keys from gpg output or something which let me cipher them, so I can put the file on Internet and nobody could be able to use my ec2 account.

I've installed Ubuntu 12.10 from PXE, using the linux & initrd.gz files and I'd like to update it to Ubuntu Desktop (with unity, the shopping len and everything in between).

I've heard that I can do it by installing the 'ubuntu-deskop' meta package, however I wonder if anyone has actually done it and if that's enough to get an identical Ubuntu installation as if I had installed it with the LiveDvd.

Thanks in advance.

I never knew what Orchestra really was, I'd like to ask, MAAS is orchestra with another name?, if not, what are the differences?

I'm running pbuilder, which setup a minimal ubuntu installation, and I'd like to retrieve some files without «wget» (it's not installed by default), since apt-get can retrieve .deb files I imagine there must be a way

I love mutt, and the mutt version shipped with Ubuntu is awesome (it even has a patched version), the only caveat I've found so far it's that I had not been able to manage several imap accounts at the same time.

Currently my mutt setup looks like this:

#$HOME/.mutt/muttrc
=== Accounts  ====

set my_decrypt=`gpg -o $HOME/.mutt/accounts/passwd.gpg.tmp -d $HOME/.mutt/accounts/passwd.gpg`

set my_first_mail_passwd=`awk '/[email protected]:/ {print $2}' $HOME/.mutt/accounts/passwd.gpg.tmp`

set my_second_mail_passwd=`awk '/[email protected]:/ {print $2}' $HOME/.mutt/accounts/passwd.gpg.tmp`

set my_rm=`rm -f $HOME/.mutt/accounts/passwd.gpg.tmp`

source $HOME/.mutt/accounts/[email protected]/[email protected]

//source $HOME/.mutt/accounts/[email protected]/[email protected]

Which means that a password.gpg file is decrypted on the fly (where my email passwords live) use it to set some vars and deleted, also a default profile is sourced, it looks like this:

#$HOME/.mutt/accounts/[email protected]/[email protected]
set folder           = "imaps://imap.foo.com"

set spoolfile        = "imaps://imap.foo.com/INBOX"

set header_cache     = "$HOME/.mutt/cache/[email protected]"

set message_cachedir = "$HOME/.mutt/cache/[email protected]"

set imap_user        = "[email protected]"

set imap_pass        = $my_first_mail_passwd

set smtp_url         = "smtp://[email protected]"

set smtp_pass        = $my_first_mail_passwd

Using this, I'm only able to use the account configured in the default profile.., I've heard that folder hooks can be used but I've no idea how to use them, and I'm also not sure if that's what I'm looking for, I'd like to just be able to source different profiles depending which email I'd like to read.., Any suggestion method is welcome.., I'd prefer a setup who don't rely on external programs who aren't part of a default Ubuntu installation.

I've a minimal Ubuntu installation, and I've heard that is possible to print to a LDP server directly with the lpr command:

   $ rlpr [email protected]

I know the lpd ip but not the queue name, so I wonder if exist a tool to request it to the LDP server, I've seen that MacOs and Ubuntu with cups are capable of guessing it.

I'm quite new to multimedia things, I'm trying to find a way to make nice screencasts, I've already been able to capture my desktop with ffmpeg:

$ ffmpeg -f alsa -ac 2 -i hw:0,0 -f x11grab -r 30 -s $(xwininfo -root | grep 'geometry' | awk '{print $2;}') -i :0.0 -acodec pcm_s16le -vcodec libx264 -vpre lossless_ultrafast -threads 0 -y out.mkv

It works pretty nice, but I'd like to add music in the background, if I add it with mencoder:

mencoder  -ovc copy -oac mix -audiofile track.mp3 out.mkv -o out.mp4

It delete the video sound, I don't want to replace it, I want to add music to my explanation, any ideas?