Ssh argument length

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.

!/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:

~/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

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.