Assign variable and redirect in bash

Question

I'm doing ad-hoc profiling on a web service that seems to maintain some state and get slower and slower until eventually things start timing out. I have a simple script that will expose this behavior:

while true
do
    RESPONSE_CODE=$( curl --config curl.config )

    if [ "$RESPONSE_CODE" -eq "200" ]; then
        echo SUCCESS
    else
        echo FAILURE
    fi
done

Along with some headers, cookies, post data, url, etc. curl.config in particular has the lines:

silent
output = /dev/null
write-out = "%{http_code}"

So the only output from curl should be the HTTP status code.

This works fine. What I'd like to do is something like this:

{ time -p RESPONSE_CODE=$(curl --config curl.config) ; } 2>&1 | awk '/real/{print $2;}'

to get a running printout of how long these queries actually take, while still saving curl's output for use in my test. But that doesn't work.

How can I capture the http status from curl AND grab the output of time so I can process both?

Jonathan Leffler · Accepted Answer · 2014-08-19 20:42:39Z

1

As written:

RESPONSE_CODE = $( curl --config curl.config )

you have spaces around the assignment which simply does not work in shell (it tries to execute a command RESPONSE_CODE with = as the first argument, etc. You need:

RESPONSE_CODE=$( curl --config curl.config )

The time built-in is hard to redirect. Since you need both HTTP status and real time, you will have to do something to capture both values. One possibility is:

set -- $( (time -p -- curl --config curl.config ) 2>&1 |
         awk '/real/{print $2} /^[0-9]+$/{print}')

which will set $1 and $2. Another is array assignment:

data=( $( (time -p -- curl --config curl.config ) 2>&1 |
         awk '/real/{print $2} /^[0-9]+$/{print}') )

The HTTP response code should appear before the time.

(Tested using sh -c 'echo 200; sleep 1' in lieu of curl --config curl.config.)

edited Aug 19, 2014 at 20:42

answered Aug 19, 2014 at 20:18

Jonathan Leffler

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3 Comments

Dathan Over a year ago

You're right about the variable assignment - it was correct in the script, and I flubbed it while redacting the script to post here. Question updated.

Dathan Over a year ago

That did the trick, aside from time on OS X lacking the -- option. Thanks!

Jonathan Leffler Over a year ago

Interesting note on portability. The absence of support for the -- option in the Mac OS X (BSD?) time command is arguably a bug (it contravenes the POSIX Utility Syntax Guidelines and specifically Guideline 10).

konsolebox · Accepted Answer · 2014-08-19 20:45:54Z

1

This should work if Curl's response is only a single line:

#!/bin/bash
RESPONSE_CODE=''
TIME=''
while read -r TYPE DATA; do
    case "$TYPE" in
    curl)
        RESPONSE_CODE=$DATA
        ;;
    real)
        TIME=$DATA
        ;;
    esac
done < <(exec 2>&1; time -p R=$(curl --config curl.config); echo "curl $R")

Or use an associative array:

#!/bin/bash
declare -A RESPONSE
while read -r TYPE DATA; do
    RESPONSE[$TYPE]=$DATA
done < <(exec 2>&1; time -p R=$(curl ...); echo "code $R") 
echo "${RESPONSE[code] ${RESPONSE[real]}"

edited Aug 19, 2014 at 20:45

answered Aug 19, 2014 at 20:19

konsolebox

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