Simple Linux and UNIX Shell Script Based System Monitoring With ping Command

Posted on in Categories Monitoring, Networking, Shell scripting last updated July 21, 2006

You can simply monitor your remote system hosted in some remote IDC. There may be many reasons for which system may out of the network. This simple script is useful to monitor your own small network at home or work.

Understanding the ping command

The ping is one of the basic and nifty command to test network connection. For example, you can send 4 ping request to cyberciti.biz with the following command:
$ ping -c 4 cyberciti.biz
$ ping -c 4 router
Output:

PING router (192.168.1.254) 56(84) bytes of data.
64 bytes from router (192.168.1.254): icmp_seq=1 ttl=64 time=1.02 ms
64 bytes from router (192.168.1.254): icmp_seq=2 ttl=64 time=0.824 ms
64 bytes from router (192.168.1.254): icmp_seq=3 ttl=64 time=0.826 ms
64 bytes from router (192.168.1.254): icmp_seq=4 ttl=64 time=0.843 ms
 
--- router ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3012ms
rtt min/avg/max/mdev = 0.824/0.880/1.027/0.085 ms

Just see output line ‘— router ping statistics —‘ and note down the ‘4 received’ field. This the key to verify that 4 packets send and received successfully. You can extract words ‘4 received’ with the following command:
$ ping -c4 router | grep 'received'
Outputs:

4 packets transmitted, 4 received, 0% packet loss, time 3012ms

Next logical step is to just get number 4 received using the awk command:
$ ping -c4 router | grep 'received' | awk -F',' '{ print $2}'
Outputs:

4 received

Last step is to just get 4 number and remove received word:
$ ping -c4 router | grep 'received' | awk -F',' '{ print $2}' | awk '{ print $1}'
Outputs:

4

Shell script to system monitoring with ping command

Now you know how to obtained received packets, it is time to automate entire process with simple script. Here is a sample shell script (download link):

#!/bin/bash
HOSTS="cyberciti.biz theos.in router"

COUNT=4

for myHost in $HOSTS
do
  count=$(ping -c $COUNT $myHost | grep 'received' | awk -F',' '{ print $2 }' | awk '{ print $1 }')
  if [ $count -eq 0 ]; then
    # 100% failed 
    echo "Host : $myHost is down (ping failed) at $(date)"
  fi
done

You can download complete working script which sends an email alert here.

Setup Cron job

In order to run this script every 30 minutes (or as per your requirements), you need to install a script as cron job:
$ chmod +x /path/to/monitorHost
Install the monitorHost script as crontab using the editor:
$ crontab -e
Append the following cronjob entry:
# Monitor remote host every 30 minutes using monitorHost
30 * * * * /home/vivek/bin/monitorHost
Save and close the file.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

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49 comment

  5. Hie
    this is an ingenious script:)
    thanks to share it
    I have just a little question.
    I didn’t find “Email ID”
    can you help me to find it please??

    thanks for your help

    Reply Report comment

  9. I commonly use this. Just another way to do it.
    if [[ $(ping -q -c 3 10.1.1.1) == @(*100% packet loss*) ]]; then
    echo “$host is down”
    else
    echo “$host is alive”
    fi

    Reply Report comment

  14. @BenV – Will your script work if $host does not exist? Typo’s happen.

    Will adding a ‘ping -c1 -w1″ enable a timeout and avoid hanging indefinitely? or is the -w not used that way?

    Reply Report comment

  16. Along a slightly different vein- I’ve got my e-mail client set to start as soon as I log in, which is often before the network is online. It then tells me it can’t find the server and decides to work off-line. This is annoying, so I added a slight modification of the above at the head of its initialisation script:

    while :
    do
    count=$(ping -c 1 imap.1and1.co.uk | grep ‘received’ | awk -F’,’ ‘{ print $2 }’ | awk ‘{ print $1 }’)
    if [ $count -eq 1 ]; then
    break
    fi
    sleep 5
    done

    Reply Report comment

  19. It works fine except i tried to use it to make sure my internet connection was still up and if the internet connection fails It can’t resolve the host so it can’t try ping to ping it. How could i add a check for this situation?

    Reply Report comment

  23. hi,
    i am doing a small program on the working of ping command in linux using icmp protocol. here is the code but its giving an error at getuid()

    #include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
char dst_addr[20];
char src_addr[20];
unsigned short in_cksum(unsigned short*,int);
void parse_argvs(char**,char*,char*);
void usage();
char *getip();
char *toip(char*);
int main(int argc, char *argv[])
{
  struct iphdr *ip;
  struct iphdr *ip_reply;
  struct icmphdr *icmp;
  struct sockaddr_in connection;
  char *packet=NULL;
  char *buffer=NULL;
  int sockfd;
  int optval;
  int addrlen;
  int siz;
  printf("%d",getuid());
  if(getuid()!=0)
{
   fprintf(stderr,"%s:rot privileges neededn",*(argv+0));
   exit(EXIT_FAILURE);
  }
  parse_argvs(argv,dst_addr,src_addr);
  strncpy(dst_addr,toip(dst_addr),20);
  strncpy(src_addr,toip(src_addr),20);
  printf("src addr is %sn",src_addr);
  printf("dest addre is %sn",dst_addr);
  packet=malloc(sizeof(struct iphdr) + sizeof(struct icmphdr));
  buffer=malloc(sizeof(struct iphdr) + sizeof(struct icmphdr));
  ip=(struct iphdr *)packet;
  icmp=(struct icmphdr *)(packet + sizeof(struct iphdr));
  ip->ihl=5;
  ip->version=4;
  ip->tos=0;
  ip->tot_len=sizeof(struct iphdr) + sizeof(struct icmphdr);
  ip->id=htons(0);
  ip->frag_off=0;
  ip->ttl=64;
  ip->protocol=IPPROTO_ICMP;
  ip->saddr=inet_addr(src_addr);
  ip->daddr=inet_addr(dst_addr);
  ip->check=in_cksum((unsigned short *)ip,sizeof(struct iphdr));
  if((sockfd=socket(AF_INET,SOCK_RAW,IPPROTO_ICMP))==-1)
  {
    perror("socket");
    exit(EXIT_FAILURE);
  }
  setsockopt(sockfd,IPPROTO_IP,IP_HDRINCL,&optval,sizeof(int));
  icmp->type=ICMP_ECHO;
  icmp->code=0;
  icmp->un.echo.id=random();
  icmp->un.echo.sequence=0;
  icmp->checksum=in_cksum((unsigned short *)icmp,sizeof(struct icmphdr));
  connection.sin_family=AF_INET;
  connection.sin_addr.s_addr=inet_addr(dst_addr);
  sendto(sockfd,packet,ip->tot_len,0,(struct sockaddr *)&connection,sizeof(struct sockaddr));
  printf("sent %d byte packet to %sn",ip->tot_len,dst_addr);
  addrlen=sizeof(connection);
  if((siz=recvfrom(sockfd,buffer,sizeof(struct iphdr) + sizeof(struct icmphdr),0,(struct sockaddr *)&connection,&addrlen))==-1)
  {
    perror("recv");
   }
  else
   {
     printf("received %d byte reply from %sn",siz,dst_addr);
     ip_reply=(struct iphdr *)buffer;
     printf("ID: %dn",ntohs(ip_reply->id));
     printf("ttl:%dn",ip_reply->ttl);
   }
   free(packet);
   free(buffer);
   close(sockfd);
   return 0;
 }


   void parse_argvs(char **argv,char *dst,char *src)
   {
     int i;
      if(!(*(argv + 1 ) ) )
      {
        usage();
        exit(EXIT_FAILURE);
      }
     if(*(argv + 1) && (!(*(argv + 2 ) ) ) )
     {
       strncpy(dst,*(argv + 1),15);
       return;
     }
     else if((*(argv + 1 ) && (* ( argv + 2 ) ) ) )
     {
       strncpy(dst,*(argv + 1 ),15);
       i=2;
       while(*(argv + i + 1 ) )
       {
         if(strncmp(*(argv + i),"-s",2)==0)
         {
           strncpy(src,*(argv + i + 1),15);
           break;
         }
         i++;
       }
     }
    }


   void usage()
   {
     fprintf(stderr, "n usage:ping [destination]  n");
     fprintf(stderr,"destination must be providedn");
    fprintf(stderr,"source is optional n n");
   }
   char * getup()
   {
     char buffer[256];
     struct hostent *h;
     gethostname(buffer,256);
     h=gethostbyname(buffer);
     return inet_ntoa(*(struct in_addr *)h->h_addr);
   }
   char * toip(char * address)
   {
     struct hostent *h;
     h=gethostbyname(address);
     return inet_ntoa(*(struct in_addr *)h->h_addr);
   }
   unsigned short in_cksum(unsigned short *addr, int len)
   {
     register int sum=0;
     u_short answer=0;
     register u_short *w=addr;
     register int nleft=len;
     while(nleft > 1)
     {
       sum+=*w++;
       nleft-=2;
     }
      if(nleft==1)
      {
        *(u_char*) (&answer)=*(u_char*)w;
        sum+=answer;
      }
      sum=(sum>>16) + (sum & 0xffff);
      sum+=(sum>>16);
      answer=~sum;
      return(answer);
     }
    Reply Report comment

  26. This is a great tutorial but there is a little problem. Your cron job won’t be executed every 30 minutes but instead 1 time per hour at 30 minute (1:30, 2:30, 3:30). To run it every 30 min, you should change the first parameter to */30.

    Reply Report comment

  29. @Константин Кръстев
    I love your line, but could you explain the bit after the “>” I don’t get that.

    It does work I just don’t know why!

    Thanks,
    Der

    Reply Report comment

  31. I like the code but think fping is better at this and easier coding.
    install apt-get install fping
    then put in the code as
    For testing if host alive just use fping -a or fping -u:
    -a show all host in your list as alive or -u shows unavailble.
    You can also predefine using a file with th -f and a filename.

    Long and short you can do what you want by adding:
    a file called something like host.txt and code would be one line such as:
    fping -ag -f /path/host.txt > results
    your host.txt would hold all hosts you want to monitor. This one line will go out and check the hosts listed and let you know everything alive in the results file. if you leave off the -a it will list the status up or down in the results. this is getting wordy and not trying to over ride the post everyone has there own way. I am just giving a quick response of an alternate way of doing it with less lines of code.

    Thanks and great job on the code,
    Robby Loyed

    Reply Report comment

  32. I think the code could be sligtly improved.

    Sending an email for each machine that is down can lead to a very high number of emails,

    Sending one email reporting just the ones that were down during the check is easier to go through and check.

    #!/bin/bash
# Simple SHELL script for Linux and UNIX system monitoring with
# ping command
# -------------------------------------------------------------------------
# Copyright (c) 2006 nixCraft project
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
# Setup email ID below
# See URL for more info:
# http://www.cyberciti.biz/tips/simple-linux-and-unix-system-monitoring-with-ping-command-and-scripts.html
# -------------------------------------------------------------------------
fail="false"
# add ip / hostname separated by white space
HOSTS="192.168.111.1 192.168.101.1 ...."
# no ping request
COUNT=5

# email report when
SUBJECT="Ping failed"
EMAILID="email here"
for myHost in $HOSTS
do
  count=$(ping -c $COUNT $myHost | grep 'received' | awk -F',' '{ print $2 }' | awk '{ print $1 }')
  if [ $count -eq 0 ]; then
    # 100% failed
    fail="true"
    failedhosts="$failedhosts $myHost"
  fi
done
  if [ $fail = "true" ]; then
        echo $failedhosts
        echo "Hosts down: $failedhosts" | mail -s "$SUBJECT" $EMAILID
  fi
    Reply Report comment

    1. Simple Script to check whether the remote host is up or down;

      ping -c 6 192.168.1.1
      if [ “`echo $?`” == 0 ]; then
      echo “192.168.1.1 is up”
      else
      echo “192.168.1.1 is down”
      fi
      sleep 10
      sh /root/script

      Execute it once and it will not stop until you kill the script , put ‘mail’ command in the script and you will receive it in your email if there is no response from the remote host.

      Thanks,

      Reply Report comment

  36. I have developed the script such that to ping it forever:

    function CheckHost()
    {
    HOSTS=”IP”
    ping=”5″
    SUBJECT=”Ping UAT $HOSTS”
    EMAILID=”MAIL ID”
    count=$(ping -s $HOSTS 56 $ping | grep “received” | awk -F, ‘{print $1 $2 $3}’)
    echo $count
    op=$(echo $count | awk ‘{print $1 $4}’)
    echo $op
    if [ $op != $ping$ping ];
    then
    echo “Host : $HOSTS Ping Failed $count” | mailx -s “$SUBJECT” $EMAILID
    fi
    echo ‘Calling CheckHost Again!’
    CheckHost
    }
    CheckHost

    Reply Report comment

  37. Hi ,

    I was looking for a way by which I can ping the remote UNIX Servers from my Local (WINDOWS) system. Any suggestions on how can this be achieved? I fear that checking the server availability from a unix server may fail if the unix server on which the check script is hosted goes down anyday.

    Aritra

    Reply Report comment

  39. Simple Script to check whether the remote host is up or down;

    ping -c 4 192.168.1.1
    if [ “`echo $?`” == 0 ]; then
    echo “192.168.1.1 is up”
    else
    echo “192.168.1.1 is down”
    fi

    execute it through cron daemon and put use mail command to receive it to your email.

    Thanks,

    Reply Report comment

  42. Hi all… I have a script that pings a server emails me if there is no response, but it does not work. Below is the script, can someone please point out what is wrong with it and how can I fix it?

    #!/bin/csh -f
set dat = `date +'%d-%m-%Y'`

set  a = `ping -c 2 -w 2 my-host`
if ($? == 0) then
        echo ""
else
        mail -s "my-host is Down on `date`" [email protected]
endif
    Reply Report comment

  43. Hi all,
    Currently i’m run centos crontab unfortunately crontab didn’t perform the job. i’m unsure which part i’m wrong, if i run manually it is working fine without any issue. kindly need you all advise.

    crontab -e
    * * * * * /bin/sh /root/scripts/check.sh

    #!/bin/sh +x
 
HOSTS="8.8.8.8 8.8.4.4"
 
# no ping request
COUNT=3
 
for myHost in $HOSTS
do
  count=$(ping -c $COUNT $myHost | grep 'received' | awk -F',' '{ print $2 }' | awk '{ print $1 }')
  if [ $count -eq 0 ]; then
    # 100% failed
        echo "$(date) Host : $myHost is down (ping failed)" >> check.log
  else
        echo "$(date) Host : $myHost is up (ping sucessful)" >> check.log
  fi
done
    Reply Report comment

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