[CJefferson]

With regards (3), my problem in shell is that it is very hard to spawn children without risking overloading the machine.

What I would like in bash is some easy way to limit the number of background processes I can spawn, and to just wait when I try to start another one until an existing one is finished.

Some simple jobs can be converted to use xargs -P, but for more complex things I end up having to do them without parallelisation, so I don't end up spawning 100s of background processes and bring my computer to it's knees.

[int0x80]

Yes ... I think that should not be allowed (bring down the machine by a non-root user process). In Linux CPU_GROUPS/MEM_GROUPS can help, and the fair scheduler has improved the situation a bit from the old days where a fork bomb will bring the machine down.

But limiting the # of spawned children is possible using not so complicated ad-hoc solutions, but I guess it depends on the specific problem.