while loop only reading the first line of hostnames in file

keif · 12-13-2013, 06:53 AM

Hello all,

I'm trying to ssh to a list of hosts one by one and run a grep command on each host. But my while loop is only reading the first line and quitting.

Code:

#!/bin/bash

while read hostName
do
ssh vision@$STORE "grep LANE_INFO vision.cnf"
done </tmp/test-hosts.txt

I read online that this might be do to ssh reading from the same file as the while loop, but I'm not sure how to get around that. Also I don't know for sure that is the issue here.

Any help is appreciated.

Thanks.

pan64 · 12-13-2013, 07:11 AM

you read values into variable hostName but uses STORE in your ssh command.

druuna · 12-13-2013, 07:16 AM

I'm assuming that the hostName vs STORE is a typo.

Have a look at these 2 solutions:

Code:

#!/bin/bash

# using a while loop
while read hostName
do
  echo $hostName
  ssh -n vision@$STORE 'grep LANE_INFO vision.cnf'
done < /tmp/test-hosts.txt

# or, using a for loop
for hostName in $( cat /tmp/test-hosts.txt )
do
  echo $hostName
  ssh vision@$STORE 'grep LANE_INFO vision.cnf'
done

keif · 12-13-2013, 07:28 AM

Quote:

Originally Posted by druuna

I'm assuming that the hostName vs STORE is a typo.

Have a look at these 2 solutions:

Code:

#!/bin/bash

# using a while loop
while read hostName
do
  echo $hostName
  ssh -n vision@$STORE 'grep LANE_INFO vision.cnf'
done < /tmp/test-hosts.txt

# or, using a for loop
for hostName in $( cat /tmp/test-hosts.txt )
do
  echo $hostName
  ssh vision@$STORE 'grep LANE_INFO vision.cnf'
done

druuna,

Yea, STORE was a typo (I tried to set hostName=STORE in an attempt to divert ssh from reading the txt file, but it didn't work).

Thanks once again for your assistance. The while loop works great. I'll have to read up on ssh -n