Bash high memory usage in simple for loop?

[Thomas Guyot-Sionnest]

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Hey there,

I just encountered some dubious behaviour... Feeding a large data set in
a "for i in..." loop doing nothing causes exponentially large memory
usage, and that memory is never freed (although is seems to be re-used
over multiple runs...)

For instance I have 68M of small numbers (1..256) separated by newlines
and that makes bash grow over 1.6G, even when ann it does inside the
loop is calling true. The only way I can free up the memory is to leave
the shell.

You can test easily with this command (you might want to limit your
memory with ulimit first to avoid trashing your system...):

$ for i in `seq 1 10000000`; do true; done

On my test system this requires 1G of memory, and memory climbs a bit
higher on additional runs but settles at 1.1G (it doesn't seem to leak
any memory part this point.
This is running:
GNU bash, version 4.1.7(2)-release (i486-slackware-linux-gnu)
On Slackware-13.1

I also verified this behaviour on:
GNU bash, version 4.1.5(1)-release (x86_64-pc-linux-gnu)
(Ubuntu Lucid)

Is this normal or expected?

Thanks

- --
Thomas
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