Re: cat as a builtin command

[Han Pingtian <hanpt@linux.vnet.ibm.com>]

On Mon, Sep 01, 2014 at 11:39:40AM -0700, Bart Schaefer wrote:
> On Sep 1,  3:53pm, Han Pingtian wrote:
> }
> } It should be 
> } 
> }     exec {file}<&0
> } 
> } right? But I get error mesage for it:
> } 
> }     localhost% (){
> }     function> local fd
> }     function> exec {fd}<&0
> }     function> read -E -u $fd
> }     function> exec {fd}<&-
> }     function> }
> }     (anon):2: 0: bad file descriptor
> }     (anon):read:3: argument expected: -u
> }     (anon):4: failed to close file descriptor 0: bad file descriptor
> 
> I'm not able to reproduce this.  Is this in a newly started shell?
> 
>     torch% (){           
>     local fd  
>     function> exec {fd}<&0
>     function> read -E -u $fd
>     function> exec {fd}<&-
>     function> }
>     hello
>     hello
>     torch% 
> 
> I *suspect* that what happened is that while you were experimenting, some
> previous "exec <&-" has already closed descriptor 0.  Closing stdin is
> not fatal to an interactive zsh, it maintains its own descriptor for ZLE
> to access /dev/tty.
> 
> E.g., if I explicitly do:
> 
> torch% exec 0<&-   
> 
> Then up-history a couple of times and:
> 
> torch% (){         
> local fd
> exec {fd}<&0
> read -E -u $fd
> exec {fd}<&-
> }
> (anon):2: 0: bad file descriptor
> (anon):read:3: argument expected: -u
> (anon):4: failed to close file descriptor 0: bad file descriptor
> torch% 
Thanks, I cannot reproduce it after a reboot now. I think you are right,
I must closed 0 before the test. Thanks so much.