Pipe a bash script into less in the script?

keysorsoze · 06-05-2007, 08:34 AM

Hi! I had a question of how to pipe output from a script into a pager such as less so we can scroll up and down to view contents. Currently I have the following script called pmxcheck.sh that checks various aspects our mail gateway. The script puts out a lot of info, I had to create another script called pmxchk.sh that basically contains the following:

#!/bin/bash

pmxcheck.sh | less

This just basically runs the script and pipes it into the less pager to prevent the output from scrolling off screen. My question is how to integrate the less pager into my original script so we don't need two files to do one thing.

Original Script

echo "-----------"
uptime
echo
#check Disk Space
echo "Disk Utilization"
echo "----------------"
df -F ufs -h
echo
#Verify all services are running
echo "Puremessage-Services currently running"
echo "--------------------------------------"
pmx-service
echo
echo "Puremessage-Updates"
echo "-------------------"
pmx-verify | egrep 'AntiSpam-Data|Blocklist-Data|Sophos-Data'
echo
echo "Postfix Queue"
echo "-------------"
mailq | grep "Request."
echo
echo "Postfix-Qshape"
echo "--------------"
/opt/pmx/postfix/sbin/pmx-qshape
echo "Postfix-Active"
echo "--------------"
echo
/opt/pmx/postfix/sbin/pmx-qshape active
echo
echo "Postfix-Deferred"
echo "----------------"
/opt/pmx/postfix/sbin/pmx-qshape deferred
echo
echo "Postfix-Incoming"
echo "----------------"
/opt/pmx/postfix/sbin/pmx-qshape incoming
echo
echo "Milter Status"
echo "-------------"
pmx-milter status

#End

Thanks for the help.

druuna · 06-05-2007, 09:11 AM

Hi,

Although I do not know the behavior of the pmx* commands, you could solve this as follows:

Code:

#!/bin/bash

function allCommands() {
  echo "-----------"
  uptime
  echo

  #check Disk Space
  echo "Disk Utilization"
  echo "----------------"
  df -F ufs -h
  echo

  #Verify all services are running
  echo "Puremessage-Services currently running"
  echo "--------------------------------------"
  pmx-service
  echo
  echo "Puremessage-Updates"
  echo "-------------------"
  pmx-verify | egrep 'AntiSpam-Data|Blocklist-Data|Sophos-Data'
  echo
  echo "Postfix Queue"
  echo "-------------"
  mailq | grep "Request."
  echo
  echo "Postfix-Qshape"
  echo "--------------"
  /opt/pmx/postfix/sbin/pmx-qshape
  echo "Postfix-Active"
  echo "--------------"
  echo
  /opt/pmx/postfix/sbin/pmx-qshape active
  echo
  echo "Postfix-Deferred"
  echo "----------------"
  /opt/pmx/postfix/sbin/pmx-qshape deferred
  echo
  echo "Postfix-Incoming"
  echo "----------------"
  /opt/pmx/postfix/sbin/pmx-qshape incoming
  echo
  echo "Milter Status"
  echo "-------------"
  pmx-milter status
  #End
}

allCommands | less

Hope this helps.

thegeekster · 06-05-2007, 09:25 AM

Hmmmm.....Off the top of my head, you might have the best luck by redirecting all output to the pager at the beginning of the output commands ......This can be accomplished a couple of different ways: one, by redirecting everything to a different file descriptor, or just simply redirecting the output straight to the pager, depending on what else the script is doing.........The canonical way is to use an extra file descriptor, like so....

Code:

#! /bin/bash

<script setup commands, such as variable assignments, etc>

exec 3>&1   # Setting FD1 (stdin) to FD3
exec 1 | less   # piping FD1 to less

<commands for output to pager go here>

exec 1>&3     # resetting stdin back to FD1
exec 3>&-      # closing off FD3

<rest of script>
exit 0

HTH

---thegeekster

thegeekster · 06-05-2007, 09:28 AM

LOL......druuna beat me to the punch.........

Now you have a couple of different ways to do it, either use a function or manipulate file descriptors.......

keysorsoze · 06-05-2007, 10:41 AM

Thank you thegeekster, and druuna your tips have solved my problem. I simply wrapped the entire script in the function as recommended and it worked perfectly.