[gentoo-user] Script Run From Cron Sometimes Leaves Defunct sh Process

[gentoo-user] Script Run From Cron Sometimes Leaves Defunct sh Process

[Drew Tomlinson]

I wrote a script to read a smbfs mounted filesystem and make symlinks to 
the files locally.  The script appears to run fine interactively and 
fine most of the time when run by cron.  I run the script every half 
hour.  Over the course of a week or so, 15 - 20 defunct sh processes 
show up in the ps output.  I've Googled and learned that the "child" (my 
script) is exiting but the "parent" (cron) is still around.  So now my 
question is "why" and what's wrong with my script to cause this 
occasional behavior.  And more importantly, how can I fix it?  :)

Thanks for your help!

Drew

--- BEGIN ---
#! /bin/sh

# 10/13/05
# This script creates symlinks to media files on Blacklamb.  Because MythTV
# needs to write it's own "." files and such, mounting a read-only share 
and
# then creating symlinks locally keeps the share on Blacklamb clean.

remote_dir="/multimedia/Pictures"
local_dir="/tv/pictures"
find_args="-iname \"*.jpg\" -or -iname \"*.gif\""

# Don't wipe out the entire directory or else MythTV has to recreate all its
#  local cache files.  Consider using find with above $find_args to remove
# symlinks and avoid listing each *.xxx explicitly.
echo -e "\nRemoving old symlinks from $local_pictures_dir..."
rm "$local_pictures_dir"/*.[Jj][Pp][Gg]
rm "$local_pictures_dir"/*.[Gg][Ii][Ff]

# Default sh delimiter is a "space" and is stored in $IFS.
# This caused $original to be truncated at the first "space" in the file 
name.
# Save $IFS and then set sh delimeter to a newline so 'for' loop works.
OLDIFS=$IFS
IFS='
'
echo -e "\nCreating new symlinks in $local_pictures_dir..."

# Search directory contained in $remote_dir using criteria in $find_args
for original in \
        $( eval "/usr/bin/find $remote_dir \( $find_args \) -print" )
        do

        # Remove $remote_dir from filename and replace remaining "/" 
with "-"
        # and "spaces" with "_".  Save in $newfile
        newfile=`echo $original | cut --delimiter="/" --fields=4- | \
                sed -e s/"\/"/-/g -e s/" "/"_"/g`

        # Create symlink from original file to $newfile in $local_dir
        # specified above.
        ln -s "$original" "$local_dir/$newfile"
       
        # Increase count by 1
        count=$(( count + 1 ))
done

# Reset $IFS to original value
IFS=$OLDIFS

# Print number of symlinks created.
echo -e "\nCreated $count symlinks."

exit
--- END ---
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Re: [gentoo-user] Script Run From Cron Sometimes Leaves Defunct sh Process

[Heinz Sporn]

Am Sonntag, den 23.10.2005, 07:36 -0700 schrieb Drew Tomlinson:
> I wrote a script to read a smbfs mounted filesystem and make symlinks to 
> the files locally.  The script appears to run fine interactively and 
> fine most of the time when run by cron.  I run the script every half 
> hour.  Over the course of a week or so, 15 - 20 defunct sh processes 
> show up in the ps output.  I've Googled and learned that the "child" (my 
> script) is exiting but the "parent" (cron) is still around.  So now my 
> question is "why" and what's wrong with my script to cause this 
> occasional behavior.  And more importantly, how can I fix it?  :)
> 
> Thanks for your help!
> 
> Drew
> 
> --- BEGIN ---
> #! /bin/sh
> 
> # 10/13/05
> # This script creates symlinks to media files on Blacklamb.  Because MythTV
> # needs to write it's own "." files and such, mounting a read-only share 
> and
> # then creating symlinks locally keeps the share on Blacklamb clean.
> 
> remote_dir="/multimedia/Pictures"
> local_dir="/tv/pictures"
> find_args="-iname \"*.jpg\" -or -iname \"*.gif\""
> 
> # Don't wipe out the entire directory or else MythTV has to recreate all its
> #  local cache files.  Consider using find with above $find_args to remove
> # symlinks and avoid listing each *.xxx explicitly.
> echo -e "\nRemoving old symlinks from $local_pictures_dir..."
> rm "$local_pictures_dir"/*.[Jj][Pp][Gg]
> rm "$local_pictures_dir"/*.[Gg][Ii][Ff]
> 
> # Default sh delimiter is a "space" and is stored in $IFS.
> # This caused $original to be truncated at the first "space" in the file 
> name.
> # Save $IFS and then set sh delimeter to a newline so 'for' loop works.
> OLDIFS=$IFS
> IFS='
> '
> echo -e "\nCreating new symlinks in $local_pictures_dir..."
> 
> # Search directory contained in $remote_dir using criteria in $find_args
> for original in \
>         $( eval "/usr/bin/find $remote_dir \( $find_args \) -print" )
>         do
> 
>         # Remove $remote_dir from filename and replace remaining "/" 
> with "-"
>         # and "spaces" with "_".  Save in $newfile
>         newfile=`echo $original | cut --delimiter="/" --fields=4- | \
>                 sed -e s/"\/"/-/g -e s/" "/"_"/g`
> 
>         # Create symlink from original file to $newfile in $local_dir
>         # specified above.
>         ln -s "$original" "$local_dir/$newfile"

Just a suggestion: insert a minimum of error handling like 

ln -s "$original" "$local_dir/$newfile"
if (( $? > 0 )) ; then logger -t "myscript" "That didn't work for some
reason ; fi

... or something else at points where the script could fail.

>        
>         # Increase count by 1
>         count=$(( count + 1 ))
> done
> 
> # Reset $IFS to original value
> IFS=$OLDIFS
> 
> # Print number of symlinks created.
> echo -e "\nCreated $count symlinks."
> 
> exit
> --- END ---
-- 
Mit freundlichen Grüßen

Heinz Sporn

SPORN it-freelancing

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Email:   heinz.sporn@sporn-it.com
         heinz.sporn@utanet.at
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         A-4540 Bad Hall
         Austria / Europe

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Re: [gentoo-user] Script Run From Cron Sometimes Leaves Defunct sh Process

[Drew Tomlinson]

On 10/24/2005 1:04 AM Heinz Sporn wrote:

>Am Sonntag, den 23.10.2005, 07:36 -0700 schrieb Drew Tomlinson:
>  
>
>>        # Create symlink from original file to $newfile in $local_dir
>>        # specified above.
>>        ln -s "$original" "$local_dir/$newfile"
>>    
>>
>
>Just a suggestion: insert a minimum of error handling like 
>
>ln -s "$original" "$local_dir/$newfile"
>if (( $? > 0 )) ; then logger -t "myscript" "That didn't work for some
>reason ; fi
>
>... or something else at points where the script could fail.
>  
>

Good idea!

Thanks,

Drew

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