Re: multi-threaded compiling

[Mischa Baars]

On Mon, Mar 11, 2024 at 7:14 PM Greg Wooledge <greg@wooledge.org> wrote:

> On Mon, Mar 11, 2024 at 06:51:54PM +0100, Mischa Baars wrote:
> > SECONDS=5; for (( i=0;i<32;i++ )); do { exit ${i}; } & pid[${i}]=${!};
> done; sleep ${SECONDS}; for (( i=0;i<32;i++ )); do wait -n ${pid[${i}]};
> e=${?}; echo "$(printf %3u ${i}) pid ${pid[${i}]} exit ${e}"; done;
> > /bin/bash: line 1: wait: 1747087: no such job
> >   0 pid 1747087 exit 127
> > /bin/bash: line 1: wait: 1747088: no such job
> >   1 pid 1747088 exit 127
>
> Without analyzing this in depth, one thing struck me immediately:
> you're using the reserved variable SECONDS, which has special semantics
> in bash.  ${SECONDS} is going to expand to an ever-increasing number,
> beginning with 5 (since that's the value you assigned), and going up
> by 1 per second that the script runs.  I'm assuming that was not your
> intention.
>

It wasn't. I modified the script and makefile accordingly.


>
> In general, any variable whose name is all capital letters *may* have
> special meaning to the shell and should not be used for general storage
> purposes in scripts.
>

Completely right again. I will definitely use these recommendations next
time I write a script or a makefile.