Bash script to check HTTP status before executing tests

Question

Hi I am trying to execute specific tests only if application is up and running (I am using docker), I am trying to achieve this with the help of bash script. What I am expecting is I need to run a loop until I receive 200 status from application, once I receive 200 script should move ahead and execute the test.I am trying bash script as follows

#!/bin/bash
urlstatus=0
until [ $urlstatus -ne 200 ]; do
urlstatus=$(curl -o /dev/null --silent --head --write-out '%{http_code}' "http://localhost:8000/animals")
echo $urlstatus
done

Execute Test if application is up & running

Please let me know what is missing in the script.

Thanks

Could you please do mention what error you are getting here? or what is not working. — RavinderSingh13
– RavinderSingh13, Commented Jun 22, 2018 at 14:51
You should do While True: and then and if statement, when urlstatus == 200 run your code and exit. — Miguel Ortiz
– Miguel Ortiz, Commented Jun 22, 2018 at 14:57
It's always not equal to 200 on the very first time it's tested -- you initialize the value to 0, so the loop doesn't need to run at all! If you want your loop to run even once, initialize urlstatus=200, not urlstatus=0. — Charles Duffy
– Charles Duffy, Commented Jun 22, 2018 at 14:59
that said, if you want to wait for 200, that's not what this code does; it waits until the value isn't 200. — Charles Duffy
– Charles Duffy, Commented Jun 22, 2018 at 15:01

Charles Duffy · Accepted Answer · 2018-06-22 15:09:20Z

5

-ne is the exact opposite of the test you actually want; to loop until the exit status is 200 you should have -eq, or even better (to avoid error messages from the comparison if a non-numeric value is present), =.

#!/bin/sh
fetchstatus() {
  curl \
    -o /dev/null \
    --silent \
    --head \
    --write-out '%{http_code}' \
    "http://localhost:8000/animals"
}

urlstatus=$(fetchstatus)          # initialize to actual value before we sleep even once
until [ "$urlstatus" = 200 ]; do  # until our result is success...
  sleep 1                         # wait a second...
  urlstatus=$(fetchstatus)        # then poll again.
done

But since curl can adjust its exit status to indicate whether a request was successful, you don't even need that. Use --fail, and you can branch directly:

#!/bin/sh
while :; do
  curl -sS --fail -o /dev/null "http://localhost:8000/animals") && break
  sleep 1 # actually give your server a little rest
done

The && break means that we break out of the loop only if the request was successful; the --fail argument to curl means that it only returns success if the server returned a non-erroneous exit status (such as 200).

edited Jun 22, 2018 at 15:09

answered Jun 22, 2018 at 15:03

Charles Duffy

299k43 gold badges441 silver badges496 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Paul Hodges Over a year ago

This could also just be until curl -sS --fail -o /dev/null "http://localhost:8000/animals"); sleep 1; done

Miguel Ortiz Over a year ago

Would 301 be considered a non-erroneous status?

Charles Duffy Over a year ago

@MiguelOrtiz, yes, unless you use -L and it redirects to something that fails. Frankly, though, any service that uses a 301 when it's not done initializing yet is misdesigned -- it's explicitly a "permanent redirection", not something that can be expected to go away after things finish booting.

Collectives™ on Stack Overflow

Bash script to check HTTP status before executing tests

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related