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Full Discussion: Why this script is not working as 'expected' when doing ssh with while read ... really confused?
Top Forums UNIX for Beginners Questions & Answers Why this script is not working as 'expected' when doing ssh with while read ... really confused? Post 303035056 by newbie_01 on Monday 13th of May 2019 06:50:08 AM
Old 05-13-2019
Why this script is not working as 'expected' when doing ssh with while read ... really confused?
Hi,

I have a script below that is running ssh <host> <command> on some servers.

Below is more or less the script. I have to modify it somehow to get rid of the 'confidential' hostnames

Code:
check_log.bash

#!/bin/bash
#

myPID=$$

parse_log ()
{
   sub="parse_log"
   host=${1}
   service=${2}

   echo
   echo "----------------------------------------------------------------"
   echo
   echo "... Parsing listener log on ${host}"

   cat /dev/null > ${sub}.${host}.tmp
   ssh ${host} find /u01/app/grid/diag/tnslsnr/${host} -name "listener*log" -print | tee -a ${sub}.${host}.tmp

   while read log
   do
      echo "     --> Searching ${log} for ${service} on ${host} ..."
      #ssh ${host} grep -i "${service}" ${log}
      #echo
   done < ${sub}.${host}.tmp

   echo
   echo "----------------------------------------------------------------"
   echo
}


########
# MAIN #
########

parse_log "host1" "test_app"
parse_log "host2" "test_app"
parse_log "host3" "test_app"

I am running the script on a mounted filesystem that is accessible to all hosts, i.e. for example /nfs/scripts. So the script is /nfs/scripts/check_log.bash and I just run it from host1 as ./check_log.bash.

So the first ssh below runs fine, it does the find and redirect the result to the .tmp file

Code:
   cat /dev/null > ${sub}.${host}.tmp
   ssh ${host} find /u01/app/grid/diag/tnslsnr/${host} -name "listener*log" -print | tee -a ${sub}.${host}.tmp

I then want to grep for a script like "test_app" from each file which is why I have the following while loop.

Code:
   while read log
   do
      echo "     --> Searching ${log} for ${service} on ${host} ..."
      #ssh ${host} grep -i "${service}" ${log}
      #echo
   done < ${sub}.${host}.tmp

So far so good, I tested and it does shows me the " Searching ..." string. However when I am now ready to run it the ssh and has uncommented the
Code:
#ssh ${host} grep -i "${service}" ${log}

. The while loop is not going thru all the file in the .tmp file, it is only doing it on the first file. It's as if after it run the first ssh it is breaking out of the while loop?

At first I thought maybe it has to do with using /bin/bash. Using /bin/ksh gives the same result.

Not sure what am doing wrong :-) Checking the .tmp file, I can see that each of them has about 6-7 files.
 

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LEARN ABOUT HPUX

ssh-argv0

SSH-ARGV0(1)                                                BSD General Commands Manual                                               SSH-ARGV0(1)

NAME

     ssh-argv0 -- replaces the old ssh command-name as hostname handling

SYNOPSIS

     hostname | user@hostname [-l login_name] [command]

     hostname | user@hostname [-afgknqstvxACNTX1246] [-b bind_address] [-c cipher_spec] [-e escape_char] [-i identity_file] [-l login_name]
     [-m mac_spec] [-o option] [-p port] [-F configfile] [-L port:host:hostport] [-R port:host:hostport] [-D port] [command]

DESCRIPTION

     ssh-argv0 replaces the old ssh command-name as hostname handling.  If you link to this script with a hostname then executing the link is
     equivalent to having executed ssh with that hostname as an argument.  All other arguments are passed to ssh and will be processed normally.

OPTIONS

     See ssh(1).

FILES

     See ssh(1).

AUTHORS

     OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen.  Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
     Theo de Raadt and Dug Song removed many bugs, re-added newer features and created OpenSSH.  Markus Friedl contributed the support for SSH
     protocol versions 1.5 and 2.0.  Jonathan Amery wrote this ssh-argv0 script and the associated documentation.

SEE ALSO

     ssh(1)

Debian Project                                                   September 7, 2001                                                  Debian Project
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