[SOLVED] Preserving Variables over SSH.

cnitin · 05-10-2013, 06:27 AM

Hi ,

I am writing a script which would first check if any database is up on the server and if any database is up it will export its name and login to database and fire few sql queries , all this will occur over ssh.

Below is my code :

Code:

/usr/bin/ssh -qn oracle@10.1.46.233 "
. $HOME/.bash_profile
ps -ef|grep pmon |grep -v grep > $HOME/dbname.txt
cd $HOME
#echo \"content of dbname\"
#cat $HOME/dbname.txt
echo \"-------------------------\"
while read inputline
        do
        echo \"----inside while loop----\"
        #echo $inputline
        echo $inputline > $HOME/test.txt
        input=`cat $HOME/test.txt |awk '{print $1}'`
        echo $input
done < $HOME/dbname.txt

#echo $dbname
#export ORACLE_SID=test
#sqlplus  \"/ as sysdba\" << EOF
#select name,open_mode from v\\\$database;
#exit;
#EOF
"

Now the problem is when i execute this script it creates dbname.txt file which contains the output of grep , but test.txt file blank ,even if i echo $inputline it shows nothing.

Below is the output.

Code:

[oracle@test ~]$ ./test.sh
content of dbname
oracle   12449     1  0 May06 ?        00:00:53 ora_pmon_test
-------------------------
----inside while loop----

As per me this issues seems to be because of variables not being able to preserve its content.

I am using RHEL 4.2 (Pretty old test server)
Please reply if any other information is required.

Please help.

Regards,
Nitin

cnitin · 05-10-2013, 07:02 AM

Hi Guys,

Please help

jpollard · 05-10-2013, 07:47 AM

I believe what you want to use is called a "here document" redirection.

From the bash manpage:

Code:

Here Documents
       This type of redirection instructs the shell to  read  input  from  the
       current source until a line containing only delimiter (with no trailing
       blanks) is seen.  All of the lines read up to that point are then  used
       as the standard input for a command.

       The format of here-documents is:

              <<[-]word
                      here-document
              delimiter

       No  parameter expansion, command substitution, arithmetic expansion, or
       pathname expansion is performed on word.  If any characters in word are
       quoted,  the  delimiter is the result of quote removal on word, and the
       lines in the here-document are not expanded.  If word is unquoted,  all
       lines  of  the here-document are subjected to parameter expansion, com‐
       mand substitution, and arithmetic expansion.  In the latter  case,  the
       character  sequence  \<newline> is ignored, and \ must be used to quote
       the characters \, $, and `.

       If the redirection operator is <<-, then all leading tab characters are
       stripped  from  input  lines  and  the line containing delimiter.  This
       allows here-documents within shell scripts to be indented in a  natural
       fashion.

The likely problem you are having is quoting...

Try replacing the command with:

Code:

usr/bin/ssh -qn oracle@10.1.46.233 <<ENDOFCOMMANDS
...
ENDOFCOMMANDS

And put your script where the "..." is.

Also - remember that things like ` will be interpreted on the local system and not on the remote. As are all substitutions of environment variables, so they will have to be escaped to prevent them from being interpreted on the wrong system.

AwesomeMachine · 05-10-2013, 07:49 AM

Maybe examine the done line.

chrism01 · 05-10-2013, 07:56 AM

It can get a bit tricky doing all that (eg setting vars to be interpreted on remote etc) from the first host.
Easiest is to write the script, then scp across ( only need to do this when script is changed), then run it remotely and capture the output

Code:

ssh user@remote "/path/to/script.sh"

By default output appears back on first host, so you can re-direct to a file if reqd and eg email it.
Use ssh auth keys if this is automated.

cnitin · 05-10-2013, 08:35 AM

Thanks a lot JPollard.

I've changed the script to below and now it works ,

Code:

/usr/bin/ssh -qn oracle@10.1.46.233 "
. \$HOME/.bash_profile
ps -ef|grep pmon |grep -v grep > \$HOME/dbname.txt
cd \$HOME
echo \"content of dbname\"
cat \$HOME/dbname.txt
echo \"-------------------------\"
while read inputline
        do
        echo \"----inside while loop----\"
        echo \$inputline
        echo \$inputline > \$HOME/test.txt
        input=\`cat \$HOME/test.txt |awk '{print $1}'\`
        echo \$input
done < \$HOME/dbname.txt

#echo $dbname
#export ORACLE_SID=test
#sqlplus  \"/ as sysdba\" << EOF
#select name,open_mode from v\\\$database;
#exit;
#EOF
"

your analysis was correct abt escaping the variables.