which package a file belongs to

Nils Kassube kassube at gmx.net
Sun Jan 18 18:49:01 UTC 2009

Matthew Flaschen wrote:
> Nils Kassube wrote:
> > Matthew Flaschen wrote:
> >> Nils Kassube wrote:
> >>> dpkg -S /usr/bin/nedit|dpkg -l $(cut -f1 -d':')
> >>
> >> Doesn't work.  But:
> >>
> >>   dpkg -l `dpkg -S /usr/bin/nedit|cut -f1 -d':'`
> >>
> >> would.
> >
> > Sorry, I don't understand why it shouldn't work. Here both commands
> > have the same output.
> Nothing is being passed to the cut command, so first you get:
> cut: -: Input/output error
> then dpkg -l gets no other parameters so prints everything.

Now its getting interesting :)

Actually I had tried the command supplied by the OP and tested what the 
output was. I didn't fully evaluate the logic of the command sequence. 
Then I modified the command to the version I posted and tested that 
version and the output was what I expected.

While your explanation seems logical, the command did work on my machine. 
Therefore I made some tests to find out how the shell works with 
pipelines and command substitution:

In a new directory make a file first:

$ touch test

How does ls works with a pipe?

$ echo hello | ls

Good - like I expected, ls ignores the hello from the pipe. Now, how does 
the combination with a command substitution work?

$ echo hello | ls $(cut -f1)
ls: cannot access hello: No such file or directory

OK, so the command substitution reads the pipeline and ls gets the output 
of the command substitution.

> Note, this is actually tested.

Like I wrote above, I have tested my version also and here it works. Could 
it be that you don't use bash but some other shell? I made the test on my 
Kubuntu 8.04 machine first and then I verified that the result is the 
same with the Ubuntu 8.10 LiveCD.


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