Custom Shell Script "missing operand"?

Buttery · 05-11-2018, 05:03 AM

I was wanting to create a simple "double click" solution for shredding areas of mine or my families drives. I'm not too familiar with shell scripts at all but the one I'm trying to use is pretty simple but I can't exactly figure out what I need to do to get it do work!

The .sh file looks something like this:
#!/bin/sh
sudo for i in <drive> ; do shred -fvzn0 $i & done

whenever I try to run it, it asks for the password then immediately closes the window. if I attempt to run the .sh from terminal then it says something along the lines of "Shred: missing shred operand".

Any ideas..?

Buttery · 05-11-2018, 05:04 AM

Not sure if it makes any difference, but I also attempting this same thing using Ubuntu and get the same issue

Turbocapitalist · 05-11-2018, 05:19 AM

You might add the following as the second line so that you can preview each line to see what really runs:

Code:

set -x

Then you might add the following after done to catch all the background processes.

Code:

wait

michaelk · 05-11-2018, 05:24 AM

In addition to the above where is <drive> defined?

Turbocapitalist · 05-11-2018, 05:28 AM

Also, the sudo is in the wrong place.

So instead of this:

Code:

sudo for i in <drive> ; 
do 
        shred -fvzn0 $i & 
done

Try this:

Code:

for i in <drive> ; 
do 
        sudo shred -fvzn0 $i & 
done

Otherwise $i will be empty because the for was run as a different user and thus in a different environment.

That will also make it easier to lock down in /etc/sudoers

Buttery · 05-11-2018, 05:29 AM

Quote:

Originally Posted by Turbocapitalist

You might add the following as the second line so that you can preview each line to see what really runs:

Code:

set -x

Then you might add the following after done to catch all the background processes.

Code:

wait

After using these suggestions it looks like the one line command is just reading "sudo for i in <drive>" and nothing passed the semi-colon.

Normally I'd do

Code:

sudo su
for i in /dev/sdb ; do shred -fvzn0 $i & done

Buttery · 05-11-2018, 05:32 AM

Quote:

Originally Posted by Turbocapitalist

Also, the sudo is in the wrong place.

So instead of this:

Code:

sudo for i in <drive> ; 
do 
        shred -fvzn0 $i & 
done

Try this:

Code:

for i in <drive> ; 
do 
        sudo shred -fvzn0 $i & 
done

Otherwise $i will be empty because the for was run as a different user and thus in a different environment.

That will also make it easier to lock down in /etc/sudoers

With this Terminal didn't even open

Turbocapitalist · 05-11-2018, 05:34 AM

The terminal should not open. That is correct.

Wind back a bit and please explain how you intend to launch this script, where you are getting your drive values from, and what you have in /etc/sudoers to lock all this down?

Buttery · 05-11-2018, 05:39 AM

I had just wanted it to be something that I can launch by double click > run in terminal

Drive volumes from disks

and no changes to /etc/sudoers

Turbocapitalist · 05-11-2018, 06:02 AM

Ok. There are at least two steps in this. First, get it working as you like it in the terminal. Then get it working via an icon using a .desktop file.

As far as step one goes, for the For Loop, are you typing in the list of drives or partitions by hand? Or are you getting them as output from a program or script?

hydrurga · 05-12-2018, 07:08 PM

If it's of any use to you, I use a recursive shred script written in bash (which I name shredd and call as a Caja action):

Code:

#!/bin/bash

function shredProcess {
  if [ -d "$1" ] ; then
    rmdir "$1"
    if [ $? -ne 0 ]; then
      echo "*** ERROR - $1 could not be deleted"
    fi
  elif [ -f "$1" ] ; then
    shred -n 1 "$1" # overwrite with random data
    sync # force sync of buffers to disk
    shred -n 0 -z -u "$1" # overwrite with zeroes and remove file
    if [ $? -ne 0 ]; then
      echo "*** ERROR - $1 could not be deleted"
    fi
  fi
}
                
for f in "$@" # handle spaces in filenames
do
  if [ -d "$f" ] ; then
    find "$f" -depth -print0 | while IFS= read -r -d '' file
    do 
      shredProcess "$file"
    done
  elif [ -f "$f" ] ; then
    shredProcess "$f"
  fi
done

ondoho · 05-13-2018, 12:58 AM

Quote:

Originally Posted by Buttery

for i in <drive> ;

this is wrong - the string '<drive>' is a pseudocode placeholder for something you need to fill in. it is NOT shell syntax.
also i'm not sure if shred works on drives or partitions. did you read its documentation?
i suspect you need "for i in <partitions>" instead.

edit: if you use the term "drive" in a windows mentality, you actually mean partitions.