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Re: How to get the default value of --max-args?

From: Peng Yu
Subject: Re: How to get the default value of --max-args?
Date: Sat, 21 Sep 2019 06:30:24 -0500

> That also depends on a few other factors like .e.g. "env headroom', see
>   https://git.sv.gnu.org/cgit/findutils.git/tree/xargs/xargs.c#n427
> from line 427 until line 510.
> I don't have Mac OS X, so I can't step through what's the limiting factor
> in your case.
> What's your actual concern?  I mean, depending on what COMMAND does, the
> overhead of calling ~10 instead of 1 process in the ideal GNU/Linux case
> for exactly that amount of arguments still looks okay to me.

I'd like to avoid external command like xargs as much as possible
because I want to relieve the burden of users in thinking how slow a
script is.

Also, in the following example, if I keep adding env variables, even
`xargs --help` can not be called. However, the environment variables
can still be accessed in bash. This means that even xargs could fail.
So it is not a reliable way to use xargs to figure out the limit. if
there is a shell native way to know limit?

$ cat main.sh
#!/usr/bin/env bash
# vim: set noexpandtab tabstop=2:

echo 10000
for i in {1..10000}; do eval "export x$i=1"; done
xargs --show-limits --no-run-if-empty < /dev/null

echo 20000
for i in {10001..20000}; do eval "export x$i=1"; done
xargs --help

declare -p x20000
$ ./main.sh
Your environment variables take up 85520 bytes
POSIX upper limit on argument length (this system): 174576
POSIX smallest allowable upper limit on argument length (all systems): 4096
Maximum length of command we could actually use: 89056
Size of command buffer we are actually using: 131072
Maximum parallelism (--max-procs must be no greater): 2147483647

./main.sh: line 11: /usr/local/bin/xargs: Argument list too long

declare -x x20000="1"


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