Ssh argument length - Revision history

Brianegge at 13:48, 10 May 2011

2011-05-10T13:48:51Z

← Older revision		Revision as of 13:48, 10 May 2011
Line 1:		Line 1:
	On Solaris 10, you can create command up to about 1MB in length.		Locally you can figure out the maximum argument length on your host. This can be limited by the shell and/or the kernel, depending on the platform. For example, on Solaris 10 in bash, you can create command up to about 1MB in length.

	<geshi lang="bash">		<geshi lang="bash">
Line 28:		Line 28:
	mid=$((mid-r))		mid=$((mid-r))
	fi		fi
			# slightly better / worse: r=$(awk "BEGIN{print int(($r/2)+0.5)}")
	r=$((r/2))		r=$((r/2))
	done		done

Brianegge at 13:30, 9 May 2011

2011-05-09T13:30:09Z

← Older revision		Revision as of 13:30, 9 May 2011
Line 81:		Line 81:
	</pre>		</pre>

	See [http://www.grymoire.com/Unix/CshTop10.txt Top Ten Reasons not to use the C shell]		See
			* [http://www.grymoire.com/Unix/CshTop10.txt Top Ten Reasons not to use the C shell]
			* [http://www.in-ulm.de/~mascheck/various/argmax/ ARG_MAX, maximum length of arguments for a new process]


	[[Category:Solaris]]		[[Category:Solaris]]
	[[Category:Bash]]		[[Category:Bash]]

Brianegge at 01:20, 18 January 2011

2011-01-18T01:20:54Z

← Older revision		Revision as of 01:20, 18 January 2011
Line 19:		Line 19:
	while [ $r -gt 0 ]; do		while [ $r -gt 0 ]; do
	printf "Checking length $mid \r"		printf "Checking length $mid \r"
	l=$(ssh $host printf "$(yes \| base64 -w 0 \| head -c$mid)" \| wc -c)		# this command only works if you have base64 and GNU versions of head
			#l=$(ssh $host printf "$(yes \| base64 -w 0 \| head -c$mid)" \| wc -c)
			# The follow command should work on older Solaris hosts - Thanks Alexis
			l=$(ssh $host printf "$(cat /dev/urandom \| tr -cd 'a-f0-9' \| dd count=1 bs=$mid)" \| wc -c)
	if [ $l -eq $mid ]; then		if [ $l -eq $mid ]; then
	mid=$((mid+r))		mid=$((mid+r))

Brianegge at 02:59, 17 July 2009

2009-07-17T02:59:00Z

← Older revision		Revision as of 02:59, 17 July 2009
Line 82:		Line 82:

	[[Category:Solaris]]		[[Category:Solaris]]
			[[Category:Bash]]

Brianegge at 05:33, 30 March 2009

2009-03-30T05:33:26Z

← Older revision		Revision as of 05:33, 30 March 2009
Line 54:		Line 54:

	If you need more than is, one could pipe the command into stdin and then execute it, or create a script on the remote side and execute that script.		If you need more than is, one could pipe the command into stdin and then execute it, or create a script on the remote side and execute that script.

			If you default shell is csh, you will get output like
			<pre>
			$ ~/bin/check-sshlength.sh everest
			Received disconnect from 10.0.0.92: 2: Bad packet length 1000044.
			Received disconnect from 10.0.0.92: 2: Bad packet length 500044.
			Word too longth 250000
			Word too longth 125000
			Word too longth 62500
			Word too longth 31250
			Word too longth 15625
			Word too longth 7813
			Word too longth 3907
			Word too longth 1954
			Word too longth 1466
			Word too longth 1222
			Word too longth 1100
			Word too longth 1039
			Word too longth 1024
			Word too longth 1020

			Maximum ssh argument length between everest and everest is 1019
			</pre>

			See [http://www.grymoire.com/Unix/CshTop10.txt Top Ten Reasons not to use the C shell]


	[[Category:Solaris]]		[[Category:Solaris]]

Brianegge: New page: On Solaris 10, you can create command up to about 1MB in length. $ getconf ARG_MAX 1048320 However, what is the max length of a command which you can execute...

2009-03-30T04:02:49Z

New page: On Solaris 10, you can create command up to about 1MB in length. <geshi lang="bash"> $ getconf ARG_MAX 1048320 </geshi> However, what is the max length of a command which you can execute...

New page

On Solaris 10, you can create command up to about 1MB in length.

<geshi lang="bash">
$ getconf ARG_MAX
1048320
</geshi>

However, what is the max length of a command which you can execute via ssh? To answer this, I wrote a basic script to test this.

<geshi lang="bash">
#!/bin/bash

# usage: <host> <arg size guess>

host=${1-localhost}
mid=${2-1048320}
r=$((mid/2))

while [ $r -gt 0 ]; do
printf "Checking length $mid \r"
l=$(ssh $host printf "$(yes | base64 -w 0 | head -c$mid)" | wc -c)
if [ $l -eq $mid ]; then
mid=$((mid+r))
else
mid=$((mid-r))
fi
r=$((r/2))
done

echo
echo "Maximum ssh argument length between $(hostname) and $host is $mid"
</geshi>

The results of the script look like:
<pre>
~/bin/check-sshlength.sh everest
Received disconnect from 10.0.0.92: 2: Bad packet length 1000044.
Received disconnect from 10.0.0.92: 2: Bad packet length 500044.
Received disconnect from 10.0.0.92: 2: Bad packet length 375036.
Received disconnect from 10.0.0.92: 2: Bad packet length 312540.
Received disconnect from 10.0.0.92: 2: Bad packet length 281292.
Received disconnect from 10.0.0.92: 2: Bad packet length 265660.
Received disconnect from 10.0.0.92: 2: Bad packet length 263708.
Received disconnect from 10.0.0.92: 2: Bad packet length 262732.
Received disconnect from 10.0.0.92: 2: Bad packet length 262252.
Received disconnect from 10.0.0.92: 2: Bad packet length 262188.
Received disconnect from 10.0.0.92: 2: Bad packet length 262156.
Received disconnect from 10.0.0.92: 2: Bad packet length 262156.

Maximum ssh argument length between everest and everest is 262111
</pre>

This makes sense as this jives with the maximum packet length of an ssh session. http://www.free.lp.se/fish/rfc.txt

If you need more than is, one could pipe the command into stdin and then execute it, or create a script on the remote side and execute that script.

[[Category:Solaris]]