Re: [Help-bash] How to make sure always run external command instead of builtin function?

[Peng Yu]

On Mon, Dec 3, 2018 at 5:22 PM Bob Proulx <address@hidden> wrote:
>
> Eric Blake wrote:
> > Peng Yu wrote:
> > > I currently use this to make sure to always run the external command.
> > > Is it the best way to do so? Thanks.
> > >
> > > "$(type -P cmd)" arg1 arg2
> >
> > env cmd arg1 arg2
> > also works
>
> There is also another way too:
>
>   (exec cmd ...)
>
> As I learned just the other day:
>
>   http://lists.gnu.org/archive/html/bug-bash/2018-09/msg00104.html
>   http://lists.gnu.org/archive/html/bug-bash/2018-09/msg00101.html
>
> Bob
>

This is good. (exec cmd) is faster.

$  ./main_ls.sh
time for ((i=0;i<300;++i))
do
    (exec ls)
done > /dev/null

real    0m2.231s
user    0m0.677s
sys    0m1.013s

time for ((i=0;i<300;++i))
do
    "$(type -P ls)"
done > /dev/null

real    0m2.742s
user    0m0.830s
sys    0m1.352s
$ cat main_ls.sh
#!/usr/bin/env bash
# vim: set noexpandtab tabstop=2:

set -v
time for ((i=0;i<300;++i))
do
    (exec ls)
done > /dev/null

time for ((i=0;i<300;++i))
do
    "$(type -P ls)"
done > /dev/null


-- 
Regards,
Peng