open file and command substitution of bash

open file and command substitution of bash

[alin.s]

I try to start emacs reading a file from a fifo, and I cannot.

I tried to do so:

exec 5< <(ls)

In this case , <(ls) returns a file descriptor, and I duplicate it in file
descriptor 5.

Then I start emacs so:

emacs /dev/fd/5

The result: File exists, but cannot be read...

This happens because emacs cannot read pipe files...

However, I suppose that emacs uses pipes for implementing processes... It
cannot read its stdin from a pipe and create a buffer with?


Thanks for any clarification.




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Re: open file and command substitution of bash

[Davis Herring]

> emacs /dev/fd/5

You could just do emacs <(ls) -- bash replaces <(ls) with something like
/dev/fd/63 anyway.

> However, I suppose that emacs uses pipes for implementing processes... It
> cannot read its stdin from a pipe and create a buffer with?

Certainly one could (in C) arrange for Emacs to open a file name and treat
it as if it were a pipe from a process.  But Emacs doesn't consider that
the same operation as visiting a file, which is what is requested when you
use file names as arguments.

Davis

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Re: open file and command substitution of bash

[alin.s]

The easiest form that I find to open the output is

R=mktemp; tee < <(ls) >${R} && emacs $R




Davis Herring wrote:
> 
>> emacs /dev/fd/5
> 
> You could just do emacs <(ls) -- bash replaces <(ls) with something like
> /dev/fd/63 anyway.
> 
>> However, I suppose that emacs uses pipes for implementing processes... It
>> cannot read its stdin from a pipe and create a buffer with?
> 
> Certainly one could (in C) arrange for Emacs to open a file name and treat
> it as if it were a pipe from a process.  But Emacs doesn't consider that
> the same operation as visiting a file, which is what is requested when you
> use file names as arguments.
> 
> Davis
> 
> -- 
> This product is sold by volume, not by mass.  If it appears too dense or
> too sparse, it is because mass-energy conversion has occurred during
> shipping.
> 
> 
> 
> 

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Re: open file and command substitution of bash

[Davis Herring]

> R=mktemp; tee < <(ls) >${R} && emacs $R

Isn't that just a complicated way of saying

ls>$x && emacs $x

?  Even if your "<(ls)" is just a placeholder for some preexisting pipe
(maybe a FIFO or something), you could just do

cat <(ls) >$x && emacs $x

and lose the extra < before "<(ls)" too, since cat doesn't need it.

Davis

-- 
This product is sold by volume, not by mass.  If it appears too dense or
too sparse, it is because mass-energy conversion has occurred during
shipping.