http-status-check

#!/bin/bash

# This shell script takes a url and an optional timeout period (the default being 30 seconds) and tests to see if the URL is live
# If there is no response immediately, this script retries every 5 seconds until a response is obtained or until the timeout period is reached.
# For this reason, this script is ideal for testing that a tomcat instances started up as expected: send a "start" command,
# then run this script which will wait whilst tomcat initializes.
# This script will return zero if the URL exists, and print a message containing the http response,
# or will return the curl exit code if the URL could not be accessed.
#
# Tony Burdett, Jan 2012

printUsage() {
 printf "Usage: %s: [-u URL] [-t timeout] args\n" $0;
 exit 2;
}

# -u arg is required (URL to ping), -t is optional to change default timeout
while getopts u:t: name
do
 case $name in
  u) url="$OPTARG";;
  t) timeout="$OPTARG";;
  ?) printUsage $0;;
 esac
done

# check which args are supplied
if [ -z "$url" ];
then
 printf "Required URL argument -u not specified\n";
 exit 2;
fi

if [ -z "$timeout" ];
then
 timeout=30;
 printf "Timeout not supplied, set to default 30 s.\n";
else
 printf "Timeout set to $timeout s.\n";
fi

# retry every 5 seconds for some length of time, $timeout 
retries=`expr $timeout / 5`;

# issue a curl command, -L follows redirects, --silent --output swallows any output, writes out http response code only
cmd="curl --max-time 120 --write-out %{http_code} --silent --output /dev/null -L $url"
printf "Testing status of '$url'...";
httpStatus="`$cmd`";
response=$?;
count=0;
# retry while we get a curl exit code of 7 (couldn't connect) or a non-200 http status, for max number of retries
while [[ ( $response = 7 || $httpStatus != 200 ) && $count < $retries ]]
do
 printf ".";
 count=$((count+1));
 sleep 5;
 httpStatus="`$cmd`";
 response=$?;
done

# check exit - if curl gave a response then we're done...
if [ $response -eq 0 ] 
then
 printf "complete!\n";
 printf "HTTP RESPONSE: $httpStatus\n";
 # ... but only exit with 0 if http response was 200
 if [ $httpStatus -ne 200 ]
 then 
   response=2;
 fi
else
 printf "failed, exited with exit code $response\n";
fi

# exit with curl response code, except where we got bad http response (then 2)
exit $response;