How to evaluate http response codes from bash/shell script?

I needed to demo something quickly today and came up with this. Thought I would place it here if someone needed something similar to the OP's request.

#!/bin/bash

status_code=$(curl --write-out %{http_code} --silent --output /dev/null www.bbc.co.uk/news)

if [[ "$status_code" -ne 200 ]] ; then
  echo "Site status changed to $status_code" | mail -s "SITE STATUS CHECKER" "[email protected]" -r "STATUS_CHECKER"
else
  exit 0
fi

This will send an email alert on every state change from 200, so it's dumb and potentially greedy. To improve this, I would look at looping through several status codes and performing different actions dependent on the result.

curl --write-out "%{http_code}\n" --silent --output /dev/null "$URL"

works. If not, you have to hit return to view the code itself.

Although the accepted response is a good answer, it overlooks failure scenarios. curl will return 000 if there is an error in the request or there is a connection failure.

url='http://localhost:8080/'
status=$(curl --head --location --connect-timeout 5 --write-out %{http_code} --silent --output /dev/null ${url})
[[ $status == 500 ]] || [[ $status == 000 ]] && echo restarting ${url} # do start/restart logic

Note: this goes a little beyond the requested 500 status check to also confirm that curl can even connect to the server (i.e. returns 000).

Create a function from it:

failureCode() {
    local url=${1:-http://localhost:8080}
    local code=${2:-500}
    local status=$(curl --head --location --connect-timeout 5 --write-out %{http_code} --silent --output /dev/null ${url})
    [[ $status == ${code} ]] || [[ $status == 000 ]]
}

Test getting a 500:

failureCode http://httpbin.org/status/500 && echo need to restart

Test getting error/connection failure (i.e. 000):

failureCode http://localhost:77777 && echo need to start

Test not getting a 500:

failureCode http://httpbin.org/status/400 || echo not a failure

Here is my implementation, which is a bit more verbose than some of the previous answers

curl https://somewhere.com/somepath   \
--silent \
--insecure \
--request POST \
--header "your-curl-may-want-a-header" \
--data @my.input.file \
--output site.output \
--write-out %{http_code} \
  > http.response.code 2> error.messages
errorLevel=$?
httpResponse=$(cat http.response.code)


jq --raw-output 'keys | @csv' site.output | sed 's/"//g' > return.keys
hasErrors=`grep --quiet --invert errors return.keys;echo $?`

if [[ $errorLevel -gt 0 ]] || [[ $hasErrors -gt 0 ]] || [[ "$httpResponse" != "200" ]]; then
  echo -e "Error POSTing https://somewhere.com/somepath with input my.input (errorLevel $errorLevel, http response code $httpResponse)" >> error.messages
  send_exit_message # external function to send error.messages to whoever.
fi

With netcat and awk you can handle the server response manually:

if netcat 127.0.0.1 8080 <<EOF | awk 'NR==1{if ($2 == "500") exit 0; exit 1;}'; then
GET / HTTP/1.1
Host: www.example.com

EOF

    apache2ctl restart;
fi

To follow 3XX redirects and print response codes for all requests:

HTTP_STATUS="$(curl -IL --silent example.com | grep HTTP )";    
echo "${HTTP_STATUS}";

i didn't like the answers here that mix the data with the status. found this: you add the -f flag to get curl to fail and pick up the error status code from the standard status var: $?

https://unix.stackexchange.com/questions/204762/return-code-for-curl-used-in-a-command-substitution

i don't know if it's perfect for every scenario here, but it seems to fit my needs and i think it's much easier to work with

this can help to evaluate http status

var=`curl -I http://www.example.org 2>/dev/null | head -n 1 | awk -F" " '{print $2}'`
echo http:$var

Another variation:

       status=$(curl -sS  -I https://www.healthdata.gov/user/login  2> /dev/null | head -n 1 | cut -d' ' -f2)
status_w_desc=$(curl -sS  -I https://www.healthdata.gov/user/login  2> /dev/null | head -n 1 | cut -d' ' -f2-)

Here comes the long-winded – yet easy to understand – script, inspired by the solution of nicerobot, that only requests the response headers and avoids using IFS as suggested here. It outputs a bounce message when it encounters a response >= 400. This echo can be replaced with a bounce-script.

# set the url to probe
url='http://localhost:8080'
# use curl to request headers (return sensitive default on timeout: "timeout 500"). Parse the result into an array (avoid settings IFS, instead use read)
read -ra result <<< $(curl -Is --connect-timeout 5 "${url}" || echo "timeout 500")
# status code is second element of array "result"
status=${result[1]}
# if status code is greater than or equal to 400, then output a bounce message (replace this with any bounce script you like)
[ $status -ge 400  ] && echo "bounce at $url with status $status"

To add to @DennisWilliamson comment above:

@VaibhavBajpai: Try this: response=$(curl --write-out \n%{http_code} --silent --output - servername) - the last line in the result will be the response code

You can then parse the response code from the response using something like the following, where X can signify a regex to mark the end of the response (using a json example here)

X='*\}'
code=$(echo ${response##$X})

See Substring Removal: http://tldp.org/LDP/abs/html/string-manipulation.html

1. Assuming you have already implemented a stop and start script for your application. Create a script as follows which checks the http status of your application url and restarts in case of 502:

httpStatusCode=$(curl -s -o /dev/null -w "%{http_code}" https://{your_url}/) if [ $httpStatusCode = 502 ]; then sh /{path_to_folder}/stopscript.sh sh /{path_to_folder}/startscript.sh fi

2. Implement a cron job to invoke this script every 5 mins. Assuming the script above has name checkBootAndRestart.sh. Then your crontab should look like- */5 * * * * /{path_to_folder}/checkBootAndRestart.sh