Re: Is there a way to make sure 141 exit status is resulted when pipeline is terminated prematurelly?

[Marco Ippolito]

yOn 06/10/2020 23:20, Peng Yu wrote:
> Hi,
>
> The following examples show that 141 is not always resulted when a
> pipeline is terminated prematurelly. But I'd like to make sure any
> script which calls a pipeline can determine whether the pipeline is
> terminated prematurally. Is there a way to obtain such info in the
> script? Thanks.
>
> $ seq 10 | head -n 3; declare -p PIPESTATUS
> 1
> 2
> 3
> declare -a PIPESTATUS=([0]="0" [1]="0")
> $ seq 10000000 | head -n 3; declare -p PIPESTATUS
> 1
> 2
> 3
> declare -a PIPESTATUS=([0]="141" [1]="0")

Buffers.

In your first example, seq is not being terminated by SIGPIPE whereas in 
your second example it is, so the PIPESTATUS is correct.

To verify this is the case, on Linux I prefix your commands with:

strace -f -e 'trace=!all' ...

If you wanted to force the signal arriving before program exit, you 
could introduce a delay, e.g.:

strace -f -e 'trace=!all' bash -c 'echo $$; while ((i++ < 4)); do echo 
$i; sleep .5; done' | head -n 3; declare -p PIPESTATUS

head would exit 0 normally after 3 lines and terminate the counting 
program via SIGPIPE.

Marco Ippolito
maroloccio@gmail.com