Can't figure out recursion problem in bash/freebsd

[David Rawling]

On 8/01/2010 8:47 AM, Bernard T. Higonnet wrote:
> echo starting in `pwd`
> for hoo in *
>   do
>     echo $hoo
>     if [ -d "$hoo" ]
>       then echo pushing $hoo; cd $hoo
>       $0
>       else echo processing $hoo
>     fi;
>   echo going to next item
>   done
> cd ..
>
> I have tried various minor variations , all to no avail.
>
> I have no doubt I'm doing something very dumb, but I'm too locked into 
> my vision to see it...
>
> All help appreciated
> Bernard Higonnet
I am probably the last person you'd want debugging your scripts, but I 
can at least reproduce the problem.

My test folder and file structure:

/tmp/test
     dir0
        dir00
           file00
        file0
     dir1
        dir11
           file11
        file1

Luckily, I think I have also derived the solution. The problem appears 
to be the directory stack. Specifically, the output of my revised 
version shows that it's not working in the right folders all the time.

#! /bin/sh

echo Starting in `pwd`

for hoo in *; do
   echo $hoo
   if [ -d "$hoo" ]; then
     echo Pushing $hoo; cd $hoo
     ($0)
   else
     echo Processing file $hoo
   fi
   echo Going to next item
done
cd ..

echo Finishing in `pwd`

By moving the cd command into the if statement, we change back into the 
correct folder at the right time (otherwise the siblings to the first 
directory cannot be found in the for loop, perhaps because the current 
directory has changed mid-execution):

test01# cat /root/recurse.sh
#! /bin/sh

echo Starting in `pwd`

for hoo in *; do
   echo Found item $hoo
   if [ -d "$hoo" ]; then
     echo Pushing $hoo
     cd $hoo
     $0
     cd ..
   else
     echo Processing file $hoo
   fi
   echo Going to next item
done

echo Finishing in `pwd`
test01#

I think it works - someone brighter than me can tell us both why :). 
Most of the changes you see there are stylistic (eg the placement of 
then/else and do/done) or were for my own clarity in figuring out what 
was being printed where.

Dave.
-- 

David Rawling
Principal Consultant

PD Consulting And Security
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