SSH in Shell to populate array with system information from remote host

Question

ssh $remote '( df -k )' > $REMOTE_SPACE
for (( i=0; i<no_dest; i++ ))
    do
        ssh $remote "( aux_free_space[i]=$( du -sk ${aux_dest[${i}]}  | cut -f 1 ) )"
    done

All work ok apart from populating the array aux_free_space[]; i think the du runs on the local host.

ssh $remote works fine
aux_free_space is initialised at the beginning
aux_dest is already populated

also tried: ssh $remote '( aux_free_space[i]=$( du -sk ${aux_mount[${i}]} | cut -f 1 ) )' — Stelios
– Stelios, Commented Nov 19, 2014 at 14:33
and ssh $remote ' aux_free_space[i]=$( du -sk ${aux_mount[${i}]} | cut -f 1 ) ' — Stelios
– Stelios, Commented Nov 19, 2014 at 14:33

John Kugelman · Accepted Answer · 2014-11-19 14:36:26Z

2

ssh $remote df -k > $REMOTE_SPACE

for ((i = 0; i < no_dest; i++)); do
    aux_free_space[i]=$(ssh $remote du -sk ${aux_dest[i]} | cut -f 1)
done

The array assignment has to be pulled out into the local shell, but the du must be done remotely. The cut can be done on either side, so to cut down on the levels of quoting you can do it locally. (If du returned a lot of output you might choose to do the cut remotely to cut down on network traffic.)

answered Nov 19, 2014 at 14:36

John Kugelman

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2 Comments

Stelios Over a year ago

Thanks for the explanation. Will keep it in mind. From what I understand in this case the cut is done remotely. If it were to be done locally would it be?: aux_free_space[i]=$(ssh $remote du -sk ${aux_dest[i]}) | cut -f 1

John Kugelman Over a year ago

As I wrote it the cut is local. To do it remotely, write aux_free_space[i]=$(ssh $remote "du -sk ${aux_dest[i]} | cut -f 1").

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