Bash while loop - break and exit (DIE script DIE!!!)

Question

All I want from this script is to ssh to the host, and check if the process is alive, and if it is not, I want the littel script to die. Does not die though. It stops, and then starts up again on the ssh is successful again. I want death though.

#!/bin/bash
iterate=0
while [ $iterate -le 20000 ]
do
   rc=$?
   ssh -q -T coolhost "ps -ef | egrep '[i]cool-process' | grep wrapper  "
   if [[  $rc -eq 0 ]] ; then
       sleep 2
       iterate=$((iterate+1 ))
   else
       break
       exit 1
   fi
done

It will iterate to 2000, however if the remote process breaks, it will not die. It will not break and exit.

this will work - but won't sleep - if I put a sleep the rc goes to 0 and is never dies. so this works but is too basic.

#!/bin/bash
set -e
while : ; do
   ssh -q -T coolhost "ps -ef | egrep '[i]cool-process' | grep wrapper" > /dev/null 2>&1
done

Instead of ps -ef | grep ..., use pgrep. This is a much more direct way to search for processes by name (note useful options like -u and -f which you may want or need). It will return a failure code if the process is not found. — John Zwinck
– John Zwinck, Commented Jan 6, 2015 at 0:27

Jonathan Leffler · Accepted Answer · 2015-01-06 00:27:56Z

2

You set rc=$? before the ssh command, and the last command was the test ([) command, which just succeeded, so when you test if [[ $rc -eq 0 ]] the answer is always 'yes, it does'.

It's best to test the status of ssh directly:

#!/bin/bash
iterate=0
while [ $iterate -le 20000 ]
do
    if ssh -q -T coolhost "ps -ef | egrep '[i]cool-process' | grep wrapper"; then
        sleep 2
        ((iterate++))
    else
        break   # or exit 1
    fi
done

edited Jan 6, 2015 at 0:27

answered Jan 6, 2015 at 0:21

Jonathan Leffler

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