Re: Checking executability for asynchronous commands

[Chet Ramey]

On 12/25/20 4:40 AM, Markus Elfring wrote:
> Hello,
>
> I am looking for another bit of clarification according to an implementation 
> detail.
>
> The manual is providing the following information.
> https://git.savannah.gnu.org/cgit/bash.git/tree/doc/bash.1?id=76404c85d492c001f59f2644074333ffb7608532#n627
>
> “…
>         If  a command is terminated by the control operator &, the shell 
> executes the command in the background in a subshell.  The shell does not wait for 
> the command to finish, and the
>         return status is 0.
> …”
>
>
> Thus I observe a behaviour like the following for a simple test with the
> software “bash 5.0.18-3.1” according to a “program” which does not exist here.
>
> elfring@Sonne:~> xy &
> [1] 4063
> xy: Befehl nicht gefunden
> [1]+  Exit 127                xy

Yes, the child process exits with status 127, but $? is set to 0, as POSIX
requires. If you want the exit status of the child process, add `wait $!'
when you are ready to use the status, which will set $? to 127.

Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/