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Top Forums UNIX for Dummies Questions & Answers Bash loops and variable scope Post 302503696 by 1skydive on Friday 11th of March 2011 02:01:22 PM
Old 03-11-2011
Bash loops and variable scope

Hi All,

I've been researching this problem and I am pretty sure that the issue is related to the while loop and the piping. There are plenty of other threads about this issue that recommend removing the pipe and using redirection. However, I haven't been able to get it working using the ssh and grep command.

Code:
#!/bin/bash
export date=`date '+%m/%d/%Y'`
ALERT=90
ADMIN=me@me.com
DIR="/tmp"
COUNT=0

function type1(){

  local host=$1
  ssh $host df -hP --exclude-type=nfs | grep -E "sd[bcd]|mapper" | grep -v VGsys | awk "{print \$5 \" \" \$1}" | while read output;
  do
    usep=$(echo $output | awk "{ print \$1}" | cut -d'%' -f1  )
    partition=$(echo $output | awk "{ print \$2 }" )
    if [ "$usep" -ge "$ALERT" ]; then
      USAGE=$(echo -e "$partition ($usep%)")
      TOTAL="$TOTAL $USAGE"
      echo $TOTAL
    fi
  done
  echo $TOTAL
  echo -e "$host\n$TOTAL\n"  >> "$DIR/servers.txt"

}

for i in server1 server2 server2; do
  type1 $i;
done


mail -s "$ALERT% Storage Report for $date" $ADMIN  < "$DIR/servers.txt"

rm "$DIR/server.txt"

As you can see, the TOTAL is available within the while loop but is then empty after the loop exits.

Any suggestions appreciated.

Thanks for you help.

---------- Post updated at 02:01 PM ---------- Previous update was at 10:35 AM ----------

Hah! So why is it, you bash (no pun intended) your head against a wall for a couple of days, trying every possible combination you can think of. No sooner you post the question, the light bulb goes off.

So, I moved the ssh command to the for loop output to a file and then used redirection for the while loop. Its not perfect, but at least I have my variables now and can work on the other issues I have.

This is what I ended up doing:

Code:
#!/bin/bash
export date=`date '+%m/%d/%Y'`
ALERT=90
ADMIN=me@me.com
DIR="/tmp"
COUNT=0

function type1(){

  local host=$1
  while read output
  do
    usep=$(echo $output | awk "{ print \$1}" | cut -d'%' -f1  )
    partition=$(echo $output | awk "{ print \$2 }" )
    if [ "$usep" -ge "$ALERT" ]; then
      USAGE=$(echo -e "$partition ($usep%)")
      TOTAL="$TOTAL$USAGE"
      echo $TOTAL
    fi
  done < "$DIR/hosts.txt"
  echo -e "$host\n$TOTAL\n"  >> "$DIR/servers.txt"

}

for i in server1 server2 server2; do
  ssh $host df -hP --exclude-type=nfs | grep -E "sd[bcd]|mapper" | grep -v VGsys | awk "{print \$5 \" \" \$1}" >> "$DIR/hosts.txt"
  type1 $i;
done


mail -s "$ALERT% Storage Report for $date" $ADMIN  < "$DIR/servers.txt"

rm "$DIR/server.txt"
rm "$DIR/hosts.txt"

Hope it helps someone else out.
 

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pssh(1) 						      General Commands Manual							   pssh(1)

NAME
pssh -- parallel ssh program SYNOPSIS
pssh [-vAiIP] [-h hosts_file] [-H [user@]host[:port]] [-l user] [-p par] [-o outdir] [-e errdir] [-t timeout] [-O options] [-x args] [-X arg] command ... pssh -I [-vAiIP] [-h hosts_file] [-H [user@]host[:port]] [-l user] [-p par] [-o outdir] [-e errdir] [-t timeout] [-O options] [-x args] [-X arg] [command ...] DESCRIPTION
pssh is a program for executing ssh in parallel on a number of hosts. It provides features such as sending input to all of the processes, passing a password to ssh, saving output to files, and timing out. OPTIONS
-h host_file --hosts host_file Read hosts from the given host_file. Lines in the host file are of the form [user@]host[:port] and can include blank lines and com- ments (lines beginning with "#"). If multiple host files are given (the -h option is used more than once), then pssh behaves as though these files were concatenated together. If a host is specified specified multiple times, then pssh will connect the given number of times. -H [user@]host[:port] --host [user@]host[:port] -H "[user@]host[:port] [ [user@]host[:port ] ... ]" --host "[user@]host[:port] [ [user@]host[:port ] ... ]" Add the given host strings to the list of hosts. This option may be given multiple times, and may be used in conjunction with the -h option. -l user --user user Use the given username as the default for any host entries that don't specifically specify a user. -p parallelism --par parallelism Use the given number as the maximum number of concurrent connections. -t timeout --timeout timeout Make connections time out after the given number of seconds. With a value of 0, pssh will not timeout any connections. -o outdir --outdir outdir Save standard output to files in the given directory. Filenames are of the form [user@]host[:port][.num] where the user and port are only included for hosts that explicitly specify them. The number is a counter that is incremented each time for hosts that are specified more than once. -e errdir --errdir errdir Save standard error to files in the given directory. Filenames are of the same form as with the -o option. -x args --extra-args args Passes a extra SSH command-line arguments (see the ssh(1) man page for more information about SSH arguments). This option may be specified multiple times. The arguments are processed to split on whitespace, protect text within quotes, and escape with back- slashes. To pass arguments without such processing, use the -X option instead. -X arg --extra-arg arg Passes a single SSH command-line argument (see the ssh(1) man page for more information about SSH arguments). Unlike the -x option, no processing is performed on the argument, including word splitting. To pass multiple command-line arguments, use the option once for each argument. -O options --options options SSH options in the format used in the SSH configuration file (see the ssh_config(5) man page for more information). This option may be specified multiple times. -A --askpass Prompt for a password and pass it to ssh. The password may be used for either to unlock a key or for password authentication. The password is transferred in a fairly secure manner (e.g., it will not show up in argument lists). However, be aware that a root user on your system could potentially intercept the password. -i --inline Display standard output and standard error as each host completes. -v --verbose Include error messages from ssh with the -i and options. -I --send-input Read input and send to each ssh process. Since ssh allows a command script to be sent on standard input, the -I option may be used in lieu of the command argument. -P --print Display output as it arrives. This option is of limited usefulness because output from different hosts are interleaved. EXAMPLE
Connect to host1 and host2, and print "hello, world" from each: pssh -i -H "host1 host2" echo "hello, world" Print "hello, world" from each host specified in the file hosts.txt: pssh -i -h hosts.txt echo "hello, world" Run a command as root with a prompt for the root password: pssh -i -h hosts.txt -A -l root echo hi Run a long command without timing out: pssh -i -h hosts.txt -t 0 sleep 10000 If the file hosts.txt has a large number of entries, say 100, then the parallelism option may also be set to 100 to ensure that the com- mands are run concurrently: pssh -i -h hosts.txt -p 100 -t 0 sleep 10000 Run a command without checking or saving host keys: pssh -i -H host1 -H host2 -x "-O StrictHostKeyChecking=no -O UserKnownHostsFile=/dev/null -O GlobalKnownHostsFile=/dev/null" echo hi EXIT STATUS VALUES
0 Success 1 Miscellaneous error 2 Syntax or usage error 3 At least one process was killed by a signal or timed out. 4 All processes completed, but at least one ssh process reported an error (exit status 255). 5 There were no ssh errors, but at least one remote command had a non-zero exit status. AUTHORS
Written by Brent N. Chun <bnc@theether.org> and Andrew McNabb <amcnabb@mcnabbs.org>. http://code.google.com/p/parallel-ssh/ SEE ALSO
ssh(1), pscp(1), prsync(1), pslurp(1), pnuke(1) February 25, 2010 pssh(1)
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