Checking host availability by using ping in bash scripts

Question

I want to write a script  that would keep checking if any of the devices in network  that should be online all day long  are really online  I tried to use ping  but  if     ping -c 1 some ip here     then   echo 1 else   echo 0 fi   gives 1 no matter if I enter valid or invalid ip address  How can I check if a specific address  or better any of devices from list of ip addresses  went offline

User · Answer

There is advanced version of ping -  fping   which gives possibility to define the timeout in milliseconds      bin bash IP  192 168 1 1  fping -c1 -t300  IP 2 gt  dev null 1 gt  dev null if          0   then   echo  Host found  else   echo  Host not found  fi

User · Answer

This is a complete bash script which pings target every 5 seconds and logs errors to a file  Enjoy     bin bash                  FILE errors txt         TARGET 192 168 0 1            touch  FILE           while true            do             DATE   date    d  m  Y  H  M  S               ping -c 1  TARGET  amp  gt   dev null             if       -ne 0     then               echo  quot ERROR  quot  DATE               echo  DATE  gt  gt   FILE             else               echo  quot OK  quot  DATE             fi               sleep 5           done

User · Answer

Ping returns different exit codes depending on the type of error   ping 256 256 256 256   echo      68  ping -c 1 127 0 0 1   echo      0  ping -c 1 192 168 1 5   echo      2   0 means host reachable  2 means unreachable

User · Answer

You don t need the backticks in the if statement  You can use this check  if ping -c 1 some ip here  amp  gt   dev null then   echo 1 else   echo 0 fi   The if command checks the exit code of the following command  the ping   If the exit code is zero  which means that the command exited successfully  the then block will be executed  If it return a non-zero exit code  then the else block will be executed

User · Answer

I liked the idea of checking a list like  for i in  cat Hostlist  do     ping -c1 -w2  i   grep  quot PING quot    awk   print  2  3   done  but that snippet doesn t care if a host is unreachable  so is not a great answer IMHO  I ran with it and wrote for i in  cat Hostlist  do   ping -c1 -w2  i  gt  dev null 2 gt  amp 1   echo  i    done  And I can then handle each accordingly

User · Answer

This seems to work moderately well in a terminal emulator window   It loops until there s a connection then stops      bin bash    ping in a loop until the net is up  declare -i s 0 declare -i m 0 while   ping -c1 -w2 8 8 8 8  amp  gt   dev null   do   echo  down   m  s   sleep 10   s s 10   if test  s -ge 60  then     s 0     m m 1    fi done echo -e  --------- gt  gt   UP   connect a speaker   lt  lt --------    a   The  a at the end is trying to get a bel char on connect   I ve been trying to do this in LXDE lxpanel but everything halts until I have a network connection again   Having a time started out as a progress indicator because if you look at a window with just  down  on every line you can t even tell it s moving

User · Answer

for i in  cat Hostlist  do     ping -c1 -w2  i   grep  quot PING quot    awk   print  2  3   done

User · Answer

I can think of a one liner like this to run  ping -c 1 127 0 0 1  amp  gt   dev null  amp  amp  echo success    echo fail   Replace 127 0 0 1 with IP or hostname  replace echo commands with what needs to be done in either case   Code above will succeed  maybe try with an IP or hostname you know that is not accessible   Like this   ping -c 1 google com  amp  gt   dev null  amp  amp  echo success    echo fail   and this  ping -c 1 lolcatz ninja  amp  gt   dev null  amp  amp  echo success    echo fail

User · Answer

up  fping -r 1  1   if   -z    up      then     printf  Host  1 not responding to ping    n      else     printf  Host  1 responding to ping   n  fi

User · Answer

FYI  I just did some test using the method above and if we use multi ping  10 requests      ping -c10 8 8 8 8  amp    dev null   echo      the result of multi ping command will be  0  if at least one of ping result reachable  and  1  in case where all ping requests are unreachable

[bash] Checking host availability by using ping in bash scripts

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