Re: Organising conditions

[hancooper]

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Monday, August 2, 2021 2:43 PM, hancooper <hancooper@protonmail.com> wrote:

> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Monday, August 2, 2021 2:23 PM, Greg Wooledge greg@wooledge.org wrote:
>
> > On Mon, Aug 02, 2021 at 01:52:00PM +0000, hancooper via wrote:
> >
> > > I am using some conditions and would like some assessments on the 
> > > following. For instance, are
> > > they all valid?
> >
> > > if [[ -d "$dir" && ! $list_raw ]]; then
> > > tmpfile=$oldfile
> > > fi
> >
> > > if [[ -d "$dir" ]] && [[ ! $list_raw ]]; then
> > > tmpfile=$oldfile
> > > fi
> >
> > > if [[ (-d "$dir") && (! $list_raw) ]]; then
> > > tmpfile=$oldfile
> > > fi
> >
> > Those three are fine. Pick whichever one you like.

Then doing

if [[ -d "$dir" && ! $list_raw ]]; then

or

if [[ -d "$dir" ]] && [[ ! $list_raw ]]; then


is simply dependent on preference, rather than functionality?



> > > if ([[ -d "$dir" && ! $list_raw ]]); then
> > > tmpfile=$oldfile
> > > fi
> >
> > This one is not advised. The parentheses create a subshell, which forks
> > a child shell process. This is simply unnecessary. It's not even adding
> > to readability.
>
> Do (-d "$dir") and (! $list_raw) also fork a subshell? I would use it for 
> readability.
> Is it fine to fork subshells when using conditions as I do? I do not know 
> much about
> whether forking of subshells in bash is good, bad, or whatever.