Read response of curl command in shell script

Question

I am writing a shell script in which I need to work on the response of an api. I called the api using curl command and trying to get its response in shell so that I can loop over response and print it. But I am not able to get the response. Here is the script:

#!/bin/bash
result=$(curl "https://example.com/test")
echo "test"
RESP=`echo $result | grep -oP "^[^a-zA-Z0-9]"`

echo "$RESP"

I am getting empty response after test. Can somebody help me over this ?

@Amandeepkaur, SSA(greetings), could you please check if your variable is not empty on first place? Do a echo "$result" and let us know then. — RavinderSingh13
– RavinderSingh13, Commented Jan 8, 2020 at 11:23
Sat Sri Akal @RavinderSingh13, I did echo "$result" just after curl statement and its empty. If I replace curl with wget then i get a file saved in my system which is having correct json response. Do I need to pass some headers with the curl ? — Amandeep kaur
– Amandeep kaur, Commented Jan 8, 2020 at 11:27
@Amandeepkaur, Cool so now we cleared first step of troubleshooting, we know our first variable itself DO NOT have any value so innocent grep can't do anything there, lemme check on something and get back to you here. — RavinderSingh13
– RavinderSingh13, Commented Jan 8, 2020 at 11:28

Adhoc · Accepted Answer · 2020-01-13 21:04:36Z

3

Try this syntax:

#!/bin/bash
result="$(curl -s 'https://example.com/test')"
echo "result: '$result'"
RESP=$(echo "$result" | grep -oP "^[^a-zA-Z0-9]")
echo "RESP:'$RESP'"

Explanation:

We store in $result the result of the page curled (-s removes the status of download and things that don't belong to the page)
We echo the content of $result between quotes, to check what we got.
We store the content of that grep command (what are you looking for btw? please leave a comment if you need Regex help)
We echo the content of $RESP between quotes, to check what we got.

edited Jan 13, 2020 at 21:04

answered Jan 13, 2020 at 20:59

Adhoc

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2 Comments

Charles Duffy Over a year ago

What's the value to the literal single-quotes? (I worry that their use leads people to assume that content has been quoted/sanitized adequately to make it safe to copy-and-paste into another command line, which isn't generally true -- as "'$foo'" only evaluates to the literal content of variable foo should that content not contain any literal single-quote characters).

Adhoc Over a year ago

I generally use single quotes when I check the contents of variables to differentiate line returns, single space ' ', empty variable '', etc. It's just a quick trick to see if your variable contains something, and by no mean a best practice like testing with -z, indeed! :D

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