Operator not found or unexpected

Question

First I want to apologize for being an absolute noob at programming, writing scripts, etc. I have a question about some code I used to run on my old FreeNAS 11.1 machine. I also created a thread back when I initiated the script. Back then I got the help and my script worked. Now I updated to FreeNAS 11.2 and get some messages and I want to know why they appear and how to fix this.

But first the Background. My script checks if any Client is online (by pinging the IP-address):

#!/bin/bash

HOST1=10.10.0.100 #Client 1
HOST2=10.10.0.101 #Client 2 
HOST3=10.10.0.102 #Client 3 
HOST4=10.10.0.103 #Client 4
HOST5=10.10.0.104 #Client 5

_exit () { 
case $1 in 
1) echo „No Shutdown – At least one PC is online“ ;; 
2) echo „No PC is online – Shutdown“ ;; shutdown -p now }

#Check if IPs are online 
if [ `ping -c 1 -i 1 $HOST1 | grep -wc 100.0%` -eq 0 ] || [ `ping -c 1 -i 1 $HOST2 | grep -wc 100.0%` -eq 0 ] || [ `ping -c 1 -i 1 $HOST3 | grep -wc 100.0%` -eq 0 ] || [ `ping -c 1 -i 1 $HOST4 | grep -wc 100.0%` -eq 0 ] || [ `ping -c 1 -i 1 $HOST5 | grep -wc 100.0%` -eq 0 ] ; then _exit 1;

#All Clients are offline, shutdown else                                                                                                                                                                                           
_exit 2 fi

The script itself works fine. If one client is online the script stops and if all clients are offline the Server shutsdown. But i get the following message when i run it manually via the Shell:

Usage: grep [OPTION]... PATTERN [FILE]...
Try `grep --help' for more information.
shutdown_check.sh: -wc not found
[: -eq: unexpected operator

When I ran it on my old Server (11.1) i did not get this message so it is interesting for my, why it now occurs.

Answer 1

There are a lot of separate, independent, unrelated bugs in the above code (making the question "too broad" to be within site rules; this community-wiki answer combines answers from the many flagged duplicates). Consider the below rewrite:

#!/bin/bash

hosts=(
  10.10.0.100 #Client 1
  10.10.0.101 #Client 2 
  10.10.0.102 #Client 3 
  10.10.0.103 #Client 4
  10.10.0.104 #Client 5
)

for host in "${hosts[@]}"; do
  if ping -c 1 -i 1 "$host" >/dev/null; then
    echo "No Shutdown - At least one PC ($host) is online"
    exit 0
  fi
done

echo "No PC is online - Shutdown"
shutdown -p now

---

So, what specifically was wrong with the original code?

• When you run [ $(...something...) -eq 0 ], you only get a valid test statement if ...something... emits exactly one word as output. When you give grep invalid syntax, it doesn't emit any output at all, so the result is [ -eq 0 ]. Since [ doesn't recognize -eq when not between two separate arguments, you have your error.
• If you quoted correctly, as in [ "$(...something...)" -eq 0 ], then you'd have a more useful error message (akin to the one given to [ "" -eq 0 ].
• Your version of grep does not recognize -wc as a valid combination of arguments.
• The use of grep was itself unnecessary; ping reflects success or failure in exit status, so one can directly run if ping ...; then.
• The syntax was broken in some other respects as well; running the original code through http://shellcheck.net/ will show them.