Re^2: how perl do 'envsubst'

[vincentaxhe]

thanks for your answer, I didn't know Path::Tiny do the work as File::Slurp, and $fh->print is same as print $fh, I have finished the script, all works great, the process substitution of shell is pipe to /dev/fd/ in essence

[NERDVANA]

Yep, you can see it in action with

$ echo <(echo foo)
/dev/fd/63

But, now I just realized there is still a mystery!

$ ls /dev/fd
0  1  2  3

So... how can a program open /dev/fd/63 if it doesn't exist?

[jo37]

So... how can a program open /dev/fd/63 if it doesn't exist?

Because it does exist at the time the command is run:

$ echo <(echo foo) $(ls /dev/fd)
/dev/fd/63 0 1 2 3 63

[NERDVANA]

Ah-ha! I forgot /dev/fd was a symlink to /proc/self/fd.

[vincentaxhe]

if run kmonad <(echo $config), could bind to /dev/fd/61; but use perl only /dev/fd/0 is guaranteed to exist, cann't change to others;