Re: [Help-bash] Prevent file descriptor inheritance

[Eric Blake]

On 08/08/2018 08:28 AM, R. Diez wrote:

> Say I am using the file in a loop. If I close the file descriptor every 
> time before I run an external tool, I have to reopen the file and seek 
> to the last read position. Not very convenient.

Not true. You can close it on a per-command basis, while it still 
remains open in the loop.  That's what the 3<- file redirection operator 
does when attached to a single command, rather than to exec.

> OK, you can also stop file descriptor inheritance at every command, but 
> this is not practical. After all, you may want to consider all external 
> commands suspect, so you would have to do that for every command after 
> opening your file.

Or do that on a group of commands.  Something like:

exec 3< mysecret
while read ...
do
  {
    process the just-read line
  } 3<-
done <3
exec 3<-

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org