Re: reading from external command

[Alex fxmbsw7 Ratchev]

sorry, a bit offtopic, but i think peng said not once thanks about helping
him

eof

On Tue, Mar 29, 2022 at 8:36 PM Peng Yu <pengyu.ut@gmail.com> wrote:

> The following pattern is commonly seen, when one wants to read some
> input and do something with the data taken in.
>
> while read -r x; do
>   results+=("$x") # somecode to change a variable that will be used
> after the while-loop
> done < <(
>   builtin printf '%s\n' a b c # some command to generate input.
>   # may be a pipeline line.
> )
> # do processing of results
>
> The problem is that the exit status of the code in <() is not
> accessible in the bash code anymore.
>
> I may use a tempfile to save the result so that I can get the exit
> status. But I prefer to avoid a file if possible.
>
> builtin printf '%s\n' a b c > tempfile # exit status can be obtained here.
>
> while read -r x; do
>   results+=("$x")
> done < tempfile
>
> A pipeline may be used in this way to obtain the status of the command
> generating the data via PIPESTATUS. But this way of coding will result
> in nested pipelines when there are multiple input data sources. Also,
> when there is error in the code generating the data fails, the
> while-loop part will not know it.
>
> builtin printf '%s\n' a b c | {
> while read -r x; do
>   results+=("$x")
> done
> # do processing of results here.
> }
>
> Is there a more elegant and efficient way to solve this problem
> without having to use a tempfile?
>
> --
> Regards,
> Peng
>
>