how to parse results from a command in bash script

Question

I would like to run a command and then check the results for the string "200 OK".

So far, I have the following bash script:

for i in $(seq 1 50)
   do
        printf "i is: $i\n"
        RESULTS="$(curl -i -H "Accept: application/json" -X GET http://localhost/test/store/widget/123 | grep -ne "200 OK")"
        if [ $RESULTS -eq 0 ]; then
                echo "GET failed with $RESULTS"
                break
        else
                echo "we're good"
        fi

done

When I run the above script, I get the following results:

i is: 1
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    85  100    85    0     0   3944      0 --:--:-- --:--:-- --:--:--  4047
gettest.sh: 8: [: 1:HTTP/1.1: unexpected operator
we're good
i is: 2
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    85  100    85    0     0   3293      0 --:--:-- --:--:-- --:--:--  3400
gettest.sh: 8: [: 1:HTTP/1.1: unexpected operator
we're good

The output that I get back from running the curl command once looks like this:

HTTP/1.1 200 OK
Date: Tue, 10 Feb 2015 13:21:18 GMT
Server: Apache/2.4.7 (Ubuntu)
X-Powered-By: PHP/5.5.9-1ubuntu4.5
Content-Length: 85
Content-Type: application/json; charset=utf-8

{"status":pass,"widgetinfo":"{\"widgetname\":\"the best widget\",\"price\":\"100.00\"}"}

Based on the above results, I have a few questions:

Why does the bash script print the stats about total time, speed etc to get the results from curl?
how should I modify the script so that unless the script fails, I only want to see the counter value (i), and a status indicating a pass. If it fails, I want the script to exit with the details of what was returned by the curl command.
why am i getting the error

gettest.sh: 8: [: 1:HTTP/1.1: unexpected operator?

Any tips? Thanks!

telemaco · Accepted Answer · 2015-02-10 13:47:28Z

1

You could get the http_code using this command

curl -s -o /dev/null -w "%{http_code}" http://www.wikipedia.org

This command prints in the stdout the http code

answered Feb 10, 2015 at 13:47

telemaco

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Comments

Tiago Lopo · Accepted Answer · 2015-02-10 13:54:01Z

If you don't want curl to print stats use -s, by the way you can use -f to exit with non zero in case of error 4xx and 5xx.

Valid request:

curl -sf example.com -o /dev/null  ; echo $?
0

404 not found:

curl -sf example.com/test ; echo $?
22

And if you want the error message -S:

curl -sfS example.com/test ; echo $?
curl: (22) The requested URL returned error: 404 Not Found
22

From the manual:

man curl | grep '\-[Ssf],' -A 3
       -f, --fail
              (HTTP) Fail silently (no output at all) on server errors. This is mostly done to better enable scripts etc to better deal with failed
              attempts. In normal cases when a HTTP server fails to deliver a document, it returns an HTML document stating so  (which  often  also
              describes why and more). This flag will prevent curl from outputting that and return error 22.
--
       -s, --silent
              Silent or quiet mode. Don't show progress meter or error messages.  Makes Curl mute.

       -S, --show-error
              When used with -s it makes curl show an error message if it fails.

So your script could look like this:

RESULTS="$(curl -sSfi -H "Accept: application/json" -X GET http://localhost/test/store/widget/123 -o /dev/null 2>&1)"
if [ $RESULTS -eq 0 ]; then
        echo "GET failed with $RESULTS"
        break
else
        echo "we're good"
fi

William Pursell · Accepted Answer · 2015-02-10 13:40:34Z

RESULTS=$(cmd) assigns the output of the command to RESULTS, not the value returned by the command. If you want to check that a particular string appears in the output, it is common to use grep (which will consume the output of command, so it will be unavailable):

if cmd | grep -q "some string"; then ...

If you want to check the result, just do:

if cmd; then echo cmd succeeded ...
else echo cmd failed ...
fi

Note that in the latter case, the output of cmd will still be written to the stdout of the script, so you may want to redirect.

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