Ping Script with filter - bash

Question

I have a text file with host names and IP addresses like so (one IP and one host name per row). The IP addresses and host names can be separated by a spaces and/or a pipe, and the host name may be before or after the IP address
10.10.10.10 HW-DL11_C023
11.11.11.11 HW-DL11_C024
10.10.10.13 | HW-DL12_C023
11.11.11.12 | HW-DL12_C024
HW-DL13_C023 11.10.10.10
HW-DL13_C024 21.11.11.11
HW-DL14_C023 | 11.10.10.10
HW-DL14_C024 | 21.11.11.11
The script below should be able to ping hosts with a common denominator e.g. DL13 (there are two devices and it will ping only those two). What am I doing wrong, as I simply can`t make it work?
The script is in the same directory as the data; I don`t get errors, and everything is formatted. The server is Linux.
pingme () {
hostfile="/home/rex/u128789/hostfile.txt"
IFS= mapfile -t hosts < <(cat $hostfile)
for host in "${hosts[#]}"; do
match=$(echo "$host" | grep -o "\-$1_" | sed 's/-//' | sed 's/_//')
if [[ "$match" = "$1" ]]; then
hostname=$(echo "$host" | awk '{print $2}')
ping -c1 -W1 $(echo "$host" | awk '{print $1}') > /dev/null
if [[ $? = 0 ]]; then
echo "$hostname is alive"
elif [[ $? = 1 ]]; then
echo "$hostname is dead"
fi
fi
done
}

Answer 1

Try adding these two lines to your code:
pingme () {
hostfile="/home/rex/u128789/hostfile.txt"
IFS= mapfile -t hosts < <(cat $hostfile)
for host in "${hosts[#]}"; do
echo "Hostname: $host" # <-------- ADD THIS LINE -------
match=$(echo "$host" | grep -o "\-$1_" | sed 's/-//' | sed 's/_//')
echo "...matched with $match" # <-------- ADD THIS LINE -------
if [[ "$match" = "$1" ]]; then
hostname=$(echo "$host" | awk '{print $2}')
ping -c1 -W1 $(echo "$host" | awk '{print $1}') > /dev/null
if [[ $? = 0 ]]; then
echo "$hostname is alive"
elif [[ $? = 1 ]]; then
echo "$hostname is dead"
fi
fi
done
}
Then when you run it, you should see a list of your hosts, at least.
If you don't then you're not reading your file successfully.
If you do, there's a problem in your per-host logic.
Congratulations! You've divided your problem into two smaller problems. Once you know which half has the problem, keep dividing the problem in half until the smallest possible problem is staring you in the face. You'll probably know the solution at that point. If not, add your findings to the question and we'll help out from there.

Answer 2

The original code doesn't handle the pipe separator or the possibly reversed hostname and IP address in the input file. It also makes a lot of unnecessary use of external programs (grep, sed, ...).
Try this:
# Enable extended glob patterns - e.g. +(pattern-list)
shopt -s extglob
function pingme
{
local -r host_denom=$1
local -r hostfile=$HOME/u128789/hostfile.txt
local ipaddr host tmp
# (Add '|' to the usual characters in IFS)
while IFS=$'| \t\n' read -r ipaddr host ; do
# Swap host and IP address if necessary
if [[ $host == +([0-9]).+([0-9]).+([0-9]).+([0-9]) ]] ; then
tmp=$host
host=$ipaddr
ipaddr=$tmp
fi
# Ping the host if its name contains the "denominator"
if [[ $host == *-"$host_denom"_* ]] ; then
if ping -c1 -W1 -- "$ipaddr" >/dev/null ; then
printf '%s is alive\n' "$host"
else
printf '%s is dead\n' "$host"
fi
fi
done < "$hostfile"
return 0
}
pingme DL13
The final line (call the pingme function) is just an example, but it's essential to make the code do something.

Answer 3

REX, you need to be more specific about your what IP's you are trying to get from this example. You also don't ping enough times IMO and your script is case sensitive checking the string (not major). Anyway,
First, check that your input and output is working correctly, in this example I'm just reading and printing, if this doesn't work fix permissions etc :
file="/tmp/hostfile.txt"
while IFS= read -r line ;do
echo $line
done < "${file}"
Next, instead of a function first try to make it work as a script, in this example I manually set "match" to DL13, then I read each line (like before) and (1) match on $match, if found I remove the '|', and then read the line into an array of 2. if the first array item is an a IP (contains periods) set it as the IP the other as hostname, else set the opposite. Then run the ping test.
# BASH4+ Example:
file="/tmp/hostfile.txt"
match="dl13"
while IFS= read -r line ;do
# -- check for matching string (e.g. dl13 --
[[ "${line,,}" =~ "${match,,}" ]] || continue
# -- We found a match, split out host/ip into vars --
line=$(echo ${line//|})
IFS=' ' read -r -a items <<< "$line"
if [[ "${items[0]}" =~ '.' ]] ;then
host="${items[1]}" ; ip="${items[0]}"
else
host="${items[0]}" ; ip="${items[1]}"
fi
# -- Ping test --
ping -q -c3 "${ip}" > /dev/null
if [ $? -eq 0 ] ;then
echo "$host is alive!"
else
echo "$host is toast!"
fi
done < "${file}"