Re: Necessary and sufficient conditions for using file descriptor redirection

[Koichi Murase]

2021年3月31日(水) 8:46 Peng Yu <pengyu.ut@gmail.com>:
> What are the necessary and sufficient conditions in which redirection
> to file descriptor should be used? Thanks.

I assume you are talking about the use case of `exec <redirections>'.

One case is that a user wants to keep the file opened among different
commands in an interactive session.

Another case is that one wants to open/close/reopen files with dynamic
conditions. Something like

while condition1; do
  if condition2; then
    exec 3> file
  fi
  if condition3; then
    exec 3>&-
  fi
done

But I agree that in many cases it can be rewritten without using `exec
redirections'. We can just sometimes write a code in a cleaner way
using `exec redirections'.

--
Koichi