Re: [Help-bash] What affects the number of arguments allowed?

[Eric Blake]

On 12/10/18 7:47 PM, Peng Yu wrote:
> Hi,
>
> The following test case runs differently on different terminals
> (tested on Mac OS X). Sometimes, it fails sometimes, it does not.
>
> Somebody says it is determined by kern.argmax Mac OS X. There are
> obviously other factors affecting the limit.

Yes, the size of the environment variables often affects the limits 
(although the effect may depend on your operating system).  That is, on 
a single system, if the kernel shares the storage used for sharing argv 
and environ from a parent process to its child, then having more (or 
longer) variables defined in the environment reduces the amount of space 
remaining for command line arguments.

> https://stackoverflow.com/questions/43305775/osx-sierra-argument-list-too-long
>
> How does bash determine this limit?

Bash doesn't. The kernel does.  Bash just reports the E2BIG that the 
kernel uses to fail an execve() with too much data to pass on to the child.

> Is there a command that one can
> predetermine what is a legitimate length instead of trying it and
> fails?

If you have GNU Findutils available, 'xargs --show-limits' tries pretty 
hard to come up with reasonable numbers.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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