bash 通过 ssh 在远程主机上运行多个命令

Question

I am trying to connect to multiple hosts in a loop and run few commands/scripts via ssh, and store results in local var. I am using a here doc but I am a bit confused on whether it should be quoted or not, as I am using a mix of local vars and remotely declared vars. What would be the proper syntax for this ? What do I need to escape?

for host in $HOSTS; do
   RESULT+=$(ssh -T $host <<EOF   
   H=`dirname $HOME`
   M=`mount | grep $H | grep nfs`
   [[ "$M" ]] && MYFILE=$WD/file1 ||  MYFILE=$WD/file2
   cd $WD && monit.sh $MYFILE
EOF
   )
done

$RESULT and $WD are local vars, while the others are remote. The result with the above is that local vars have the expected values, while all the remotely declared vars are empty ($H , $M , $MYFILE..) If I enclose EOF in single quotes, the result is somehow reversed : $WD is empty, while $H and $M get proper values ($MYFILE also but without the $WD part)

Many thanks

Answer 1

Short answer: escape (with a backslash) every $ and backtick that you want interpreted on the remote computer. Actually, I'd recommend replacing the backticks with $( ) (and then escaping the $ ). I haven't tested, but this should do it:

for host in $HOSTS; do
   RESULT+=$(ssh -T $host <<EOF   
   H=\$(dirname \$HOME)
   M=\$(mount | grep \$H | grep nfs)
   [[ "\$M" ]] && MYFILE=$WD/file1 ||  MYFILE=$WD/file2
   cd $WD && monit.sh \$MYFILE
EOF
   )
done

Without the escapes, everything was getting interpreted by the local shell before it was sent to the remote system. When you quoted EOF , that told the local shell not to do any interpretation at all, so the local variable ( $WD ) didn't get substituted.

Answer 2

You can use below bash script:

for s in $(cat host.txt); do
   ssh root@${s} 'bash -s' < /tmp/commands.sh
done