Re: finding a dependency chain

[davidson@ling.ohio-state.edu]

On Thu, 4 Sep 2014, davidson@ling.ohio-state.edu wrote:

> On Wed, 3 Sep 2014, Rob Owens wrote:
>
> > ----- Original Message -----
> > > From: "Kelly Clowers" <kelly.clowers@gmail.com>
> > >
> > > On Tue, Sep 2, 2014 at 1:44 PM, Rob Owens <rowens@ptd.net> wrote:
> > > > I'm trying to figure out, for example, what causes brasero to
> > > > ultimately depend on systemd.  I found a utility called debtree,
> > > > but it produces too much output to be of use to me -- it shows all
> > > > dependency chains starting at brasero, but I am only interested in
> > > > the one that ends at systemd.
> > > >
> > > > Can anybody suggest another utility, or maybe the proper syntax to
> > > > make debtree do what I want?
> > > >
> > > > Thanks
> > > >
> > > > -Rob
> > >
> > > I just used vim to search through debtree's .dot output (for such a
> > > complex thing, way easier than trying to look at the image file),
> > > and then followed up by looking around in aptitude interactive
> > > mode.
> > Thanks.  That is much easier than looking at the image file!
> >
> > I'd still like to find a method to specify the start point and end
> > point, and get output of a single dependency chain.  If anybody
> > knows a way, please post it.
>
> seems like this pipeline
>
> $ apt-cache --recurse -i depends brasero |tac
>
> yields the elements in question, and in a convenient order (children
> before parents), but with a whole bunch of irrelevance interleaved.
>
> piping it to something like the following clears away the irrelevant
> parts:

note the careful choice of words above: "*something like*"

> $ cat above_kludge
> #!/bin/bash
>
> pattrn=$1
>
> while read line
> do if [[ $line =~ ^${pattrn}$ ]]                  # Found node C.
>     then echo $line                               # Admit node C to output.
>         pattrn=$line                              # Ground the pattern.
>     else if [[ $line =~ [[:blank:]]${pattrn}$ ]]  # Found node C listed
>                                                   # above its parent.
>     then pattrn='[[:alnum:][:punct:]]*'           # Seek the parent.
>     fi
>     fi
> done

did some more tests this morning.  ouch.  above kludge has problems.

version below works better:

  #!/bin/bash

  seek_parent=1
  pattrn=$1

  while IFS='' read line
  do
      if [[ $seek_parent -eq 1 ]] && [[ $line =~ ^${pattrn}$ ]]
      then
          echo "$line"
          pattrn=$line
          seek_parent=0
      elif [[ $seek_parent -eq 0 ]] && [[ $line =~ [[:space:]]${pattrn}$ ]]
      then
          pattrn=[[:alnum:][:punct:]]+
          seek_parent=1
      fi
  done

> so, like this:
>
> $ apt-cache --recurse -i depends brasero |tac |above_kludge '.*systemd.*'

er, no.  that won't work in general.  for better results, replace '.'
on the line above with '[[:alnum:][:punct:]]'.

so, more like this:

  $ apt-cache --recurse -i depends brasero |tac |\
    above_kludge '[[:alnum:][:punct:]]*systemd[[:alnum:][:punct:]]*'

-wes

> libsystemd-login0
> dbus
> udisks
> libgdu0
> gvfs-daemons
> gvfs
> brasero
>
> while in general there might be multiple paths, above kludge will find
> just one of them.
>
> -wes