Help with either bash or find...

[Dan Thurman]

It has been awhile since I have been programming in
bash or using the 'find' command and what I am trying
to do is to figure out how to run a command to decode
all my .mpc files into wav as follows:
 
1. Find all MPC files
2. Run each file through mppdec
 
I tried to do this using the 'find' command or even with a
bash script.
 
Using find:
========
find *.mpc -type f -exec mppdec '{}' `echo {} | sed s/.mpc/.wav` \;
** fails because you cannot use {} more than once and also exec is mangled.
 
I recalled using xargs from my past, but cannot remember how to do it.
 
find *.mpc -type f -print0 | xargs ?????
 
Since I had used find/xargs in the past, I have not encountered cases where
filenames can have spaces or other characters embedded, so this is new
for me.  I was not able to get around this issue with find nor with bash scripts.
 
Using bash:
=========
#!/bin/bash
 
for i in $*
do
  F=`echo $i | sed s/.mpc//`
  mppdec $F+".mpc" $F+".wav"
done
 
Any ideas?
 
Thanks-
Dan

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[Bill Davidsen]

Gordon Messmer wrote:
>  Todd Zullinger wrote:
> > I think something similar with xargs would work too:
> >
> > find -name '*.mpc' -print0 | \
> >     xargs -0 -i mppdec "{}" "`echo {} | sed s/.mpc/.wav`"
> >   
>  
>  No, because the section in backticks would be executed by the shell, 
>  before xargs.
>  
>  xargs can't be used to run anything with shell substitution.  It doesn't 
>  call system().
>   
It's ugly to use substitution, but being pedantic you can use "bash -c 
cmd" and maybe "exec" to do what you want.

Note that I never actually *do* it that way, I'm just noting that if you 
insist on that solution it isn't impossible, just ugly.

-- 
Bill Davidsen <davidsen(a)tmr.com&gt;
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot

[Todd Zullinger]

Gordon Messmer wrote:
>  Todd Zullinger wrote:
> > I think something similar with xargs would work too:
> >
> > find -name '*.mpc' -print0 | \
> >     xargs -0 -i mppdec "{}" "`echo {} | sed s/.mpc/.wav`"
> >
>
>  No, because the section in backticks would be executed by the shell,
>  before xargs.
>
>  xargs can't be used to run anything with shell substitution.  It
>  doesn't call system(). 
Thanks for clarifying Gordon.  I wasn't positive it would work.  I
tend to use for | while more often when I need to do something
individually for each line/file/arg.

-- 
Todd        OpenPGP -> KeyID: 0xBEAF0CE3 | URL: www.pobox.com/~tmz/pgp
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The most useful piece of learning for the uses of life is to unlearn
what is untrue.
    -- Antisthenes

[Gordon Messmer]

Daniel Challen wrote:
>  for musepack_file in $(find -name \*.mpc -type f) ; do
>  	mppdec "$musepack_file" "$(echo $musepack_file | sed s/mpc$/wav/)"
>  done
>     
Doesn't work for files with spaces in their names.  Your second example 
should work, though.

>  or, using xargs *might* work:
>
>  find -print0 -name \*.mpc -type f | xargs -0 -I song mppdec song song.wav
>
>  but I think you will end up with songname.mpc.wav as the ouput
>     
Yes, you will.

>  otherwise it appears mppdec has a limited batch mode:
>
>  mppdec --wav $(find -name \*.mpc -type f) name_of_output_directory/
>     
Also won't work with files that contain spaces in their names.

[Gordon Messmer]

Todd Zullinger wrote:
>  I think something similar with xargs would work too:
>
>  find -name '*.mpc' -print0 | \
>      xargs -0 -i mppdec "{}" "`echo {} | sed s/.mpc/.wav`"
>     
No, because the section in backticks would be executed by the shell, 
before xargs.

xargs can't be used to run anything with shell substitution.  It doesn't 
call system().

[Daniel Challen]

I forgot to add: I assume you are aware that musepack is a lossy
codec/format and so decoding to Microsoft wave or some lossless
compressed format will not get the discarded data back...

- Dan
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[Daniel Challen]

Assuming your input files are in various directories:

for musepack_file in $(find -name \*.mpc -type f) ; do
	mppdec "$musepack_file" "$(echo $musepack_file | sed s/mpc$/wav/)"
done

otherwise, if they're all in one place:

for musepack_file in *.mpc ; do
	mppdec "$musepack_file" "$(basename $musepack_file .mpc).wav"
done

should do the right thing

or, using xargs *might* work:

find -print0 -name \*.mpc -type f | xargs -0 -I song mppdec song song.wav

but I think you will end up with songname.mpc.wav as the ouput

otherwise it appears mppdec has a limited batch mode:

mppdec --wav $(find -name \*.mpc -type f) name_of_output_directory/

hope that helps

- Dan
-- 

This email and any files transmitted with it are confidential and intended solely for the
use of the individual or entity to whom they are addressed. This communication may be
legally privileged. If you are not the intended recipient, please be advised that you have
received this email in error and that any use, dissemination, forwarding, printing or
copying of this email is strictly prohibited. If you have received this email in error,
please notify the OCSL switchboard on [phone].  OCSL Registered Office: East
House, New Pound Common, Wisborough Green, West Sussex, RH14 0AZ.  Registered No: 2563193

[Todd Zullinger]

Daniel B. Thurman wrote:
>  It has been awhile since I have been programming in
>  bash or using the 'find' command and what I am trying
>  to do is to figure out how to run a command to decode
>  all my .mpc files into wav as follows:
>  
>  1. Find all MPC files
>  2. Run each file through mppdec
>  
>  I tried to do this using the 'find' command or even with a
>  bash script.
>  
>  Using find:
>  ========
>  find *.mpc -type f -exec mppdec '{}' `echo {} | sed s/.mpc/.wav` \;
>  ** fails because you cannot use {} more than once and also exec is
>  mangled.
>  
>  I recalled using xargs from my past, but cannot remember how to do
>  it.
>  
>  find *.mpc -type f -print0 | xargs ?????
>  
>  Since I had used find/xargs in the past, I have not encountered
>  cases where filenames can have spaces or other characters embedded,
>  so this is new for me.  I was not able to get around this issue with
>  find nor with bash scripts. 
Something like this perhaps:

find -name '*.mpc' | while read mpc; do
    wav="${mpc/.mpc/.wav}"
    mppdec "$mpc" "$wav"
done

That would find all the .mpc files and loop through them line by line,
reading the filename into the mp3 variable.  Then a little bash
substitution replace .mpc with .wav and creates a wav var.  Finally,
mppdec is called to decode them.

I think something similar with xargs would work too:

find -name '*.mpc' -print0 | \
    xargs -0 -i mppdec "{}" "`echo {} | sed s/.mpc/.wav`"

Neither of these are tested, so if it breaks, the pieces are yours to
cherish.

-- 
Todd        OpenPGP -> KeyID: 0xBEAF0CE3 | URL: www.pobox.com/~tmz/pgp
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The kind of man who wants the government to adopt and enforce his
ideas is always the kind of man whose ideas are idiotic.
    -- H. L. Mencken