Whats the best way to achieve the following?
I want my script to find out which postion the host its running on is in a list of hosts.
thisHost=$(hostname)
machineList="pc02 server03 host01 server05"
So if thisHost=host01 I would get back postion 3.
The machine list would never be contain more than 10 items.
I could do a comparison match in a for loop but would like to know if there is a better way ?
If you need to check many hosts, you can prepare a better structure for faster lookup: an associative array:
#! /bin/bash
machineList='pc02 server03 host01 server05'
declare -A machine_number
i=1
for machine in $machineList ; do
machine_number[$machine]=$((i++))
done
thisHost=host01
echo ${machine_number[$thisHost]}
You can also use external tools:
read n _rest < <(echo "$machineList"
| tr ' ' '\n'
| nl
| grep -Fw "$thisHost")
echo $n
Bash solution:
thisHost="host01"
machineList="pc02 server03 host01 server05"
machineListArr=($machineList)
for i in "${!machineListArr[@]}"; do
[ "$thisHost" = "${machineListArr[$i]}" ] && echo "position: $((i+1))"
done
The output:
position: 3
Awk one-line solution:
thisHost="host01"
machineList="pc02 server03 host01 server05"
awk -v RS=" " -v h="$thisHost" '$0==h{ print NR }' <<<"$machineList"
The output:
3
(1) An inexpensive one-liner:
host='host01'
machineList="pc02 server03 host01 server05"
wc -w <<< ${machineList/%${host}*/dummy}
Substitute the rest of the list beginning with $host with dummy and count the words with wc.
(2) Pure Bash:
host='host01'
machineList="pc02 server03 host01 server05"
shortList=( ${machineList/%${host}*/dummy} )
echo ${#shortList[@]}
Shorten the list as shown above and return the number of elements of the array shortList.
The output is 3 in both solutions.
