Wrong return of ping command

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Taking into account that the ${parameters} is an array that can contain valid IP addresses or not, I wrote the following code: 

  for ((i=0; i<$#; i++)); do
        eval "arg=\${$i}" 
        ping ${parameters[i]} -c1 -q &>/dev/null
        if [ $? == 0 ]
            then
            echo "ok" 
        else
            echo "fail"
        fi
    done

It turns out that the return $? always seems to contain the value 0, even when the IP passed on ${parameters[i]} is not valid.

Any idea?

c shell shell-script

  • The for is iterating over the number of script arguments $#, would not be ${#parameters[@]} to iterate on the array? I think the eval... is not necessary.

  • In this case, it makes no difference whether we are iterating over the parameters or over the array. But, even making this change, the error persists.

  • The script here worked, that IP for example is not valid and even then returns "ok"?

  • any Ip, type 8.8.8.asdf

  • The error code may vary depending on the result of ping: Success: 0; No Response: 1; Other Errors: 2.

1 answer

2


Error code returned by utility ping may vary depending on the occurrence:

Success: 0

Timed-out: 1

Unreachable Host: 2

So, it follows example (tested) of a script capable of solving your problem:

#!/bin/bash

IP_LIST=( 0.0.0.0
          255.255.255.255
          xxx.xxx.xxx.xxx
          127.0.0.1
          172.217.29.46
          191.239.213.197
          17.172.224.47
          198.175.116.54 )

for ((i = 0; i < ${#IP_LIST[@]}; i++)); do

    ping -q -c1 "${IP_LIST[i]}" &>/dev/null

    case "$?" in
        '0') STATUS="OK" ;;
        '1') STATUS="TIMEOUT" ;;
        '2') STATUS="INALCANCAVEL" ;;
          *) STATUS="ERRO" ;;
    esac

    echo "IP: ${IP_LIST[i]} [${STATUS}]"

done

Exit:

IP: 0.0.0.0 [OK]
IP: 255.255.255.255 [INALCANCAVEL]
IP: xxx.xxx.xxx.xxx [INALCANCAVEL]
IP: 127.0.0.1 [OK]
IP: 172.217.29.46 [TIMEOUT]
IP: 191.239.213.197 [TIMEOUT]
IP: 17.172.224.47 [TIMEOUT]
IP: 198.175.116.54 [TIMEOUT]

A more reliable and robust method to solve your problem would be through the availability rate of each list IP.

The following is an example capable of calculating the availability rate of Ips in a list:

#!/bin/bash

IP_LIST=( 8.8.8.8
          127.0.0.1
          10.1.1.19
          172.217.29.46
          191.239.213.197
          17.172.224.47
          198.175.116.54 )

for ((i = 0; i < ${#IP_LIST[@]}; i++)); do

    PCKT_LOSS=$(ping -q -c5 "${IP_LIST[i]}" | grep -oP '\d+(?=% packet loss)')

    echo "IP: ${IP_LIST[i]} [Disponibilidade: $[100 - ${PCKT_LOSS}]%]"

done

Exit:

IP: 8.8.8.8 [Disponibilidade: 0%]
IP: 127.0.0.1 [Disponibilidade: 100%]
IP: 10.1.1.19 [Disponibilidade: 100%]
IP: 172.217.29.46 [Disponibilidade: 0%]
IP: 191.239.213.197 [Disponibilidade: 0%]
IP: 17.172.224.47 [Disponibilidade: 0%]
IP: 198.175.116.54 [Disponibilidade: 0%]

I hope I’ve helped!

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