[pocket-linux] some discrepancies in 6.3.4, 6.3.5?

[David Horton]

rainer wrote:

> hello,
>
> tried to send this problem on thursday from pine but it hasn't seemed 
> to have arrived, please excuse the repeat if it does!
>
> i was continuing with ch. 6 when i noticed a few possible 
> discrepancies (?);
>
> in 6.3.4 for the init.d/rc script we have,
>
> # Execute the kill scripts first.
>  for SCRIPT in $SCRIPT_DIR/K*; do
>    if [ -x "$SCRIPT" ]; then
>      $SCRIPT stop;
>    fi;
>  done;
> #
> # Do the Start scripts last.
>  for SCRIPT in $SCRIPT_DIR/S*; do
>    if [ -x $SCRIPT ]; then
>      $SCRIPT start;
>    fi;
>  done;
>
> inside the square brackets we have "$SCRIPT" in kill and $SCRIPT in 
> start.
> is this intentional?
>
> in 6.3.5 in the modified local_fs script we have,
>
>
> start)
>  echo "Checking local filesystem integrity."
>  fsck -ATCp
>  if [ $(($?)) -gt $((1)) ]; then
>
> but the original local_fs from 5.3.7 has
>
>
> fsck -ATCp
> if [ $? -gt 1 ]; then
>
> my understanding is this part didn't need any modification in the 
> updated script, again is this intentional?
>
>
> thanks


These are both unintentional typos.  Neither one will break anything, 
but you're right that it does look confusing.

[ -x $SCRIPT ]; and [ -x "$SCRIPT" ]; are essentially the same, but 
using the double quotes explicitly tells BASH to expand any characters 
like * ? or ~ into filenames.  It's probably best to use the double 
quotes and not rely on BASH to guess if it should expand or not.

[ $(($?)) -gt $((1)) ]; and [ $? -gt 1 ]; are the same, but the former 
is much more confusing to look at.  The $(( )) notation tells BASH to 
treat what is in the parentheses as a numerical value.  However this is 
redundant because -gt (greater than) is a numerical operator and using 
it implies that we are dealing with numbers.  So it is best to use the 
easier to read [ $? -gt 1 ]; format.

If you want to gain some more insight into the notation the BASH manpage 
has more detailed descriptions.  There are also some manpages for the 
original Bourne shell that are much more concise.  You can find these on 
the web or on an older, non-Linux, Unix box.  When searching it is 
important to note that many times the Bourne shell is called bsh instead 
of just sh.

Dave