bash string interpolation returns empty string [duplicate]

Question

I am working on simple curl POST script and I have problem with string interpolation of a variable that is initialized with data from a script. Let me describe it:

#!/bin/bash

EMAIL=$(source ./random_email_generator.sh) #this generates some random string 
echo "$EMAIL" #here email is printed well
curl --insecure --header "Content-Type: application/json" \
  --request POST \
  --data '{"email":'"$EMAIL"',"password":"validPassword"}' \ #problem lies here because email is always empty string 
 http:/ticketing.dev/api/users/signup

To sum up, there is a lot of quotes and double quotes here and it is abit mixed up, how can I resolve value of EMAIL in place of json body?

Thanks in advance

Could you run this with bash -x yourscript and edit the question to include the output? Your code isn't exactly following best practices -- a sufficiently surprising email address could generate invalid JSON -- but it should work, even so. — Charles Duffy
– Charles Duffy, Commented Jan 5, 2021 at 18:38
email="[email protected]" ; echo $(printf '{"email":"%s"}' $email) — Abelisto
– Abelisto, Commented Jan 5, 2021 at 18:44
@Abelisto, ...well, that's got its own problems, owing mostly to lack of quotes. See what happens if you have a character from IFS present in your email address (f/e: IFS=.; email='[email protected]'; echo $(printf '{"email": "%s"}' $email)); and that's ignoring what happens if you have a value that could be parsed as a glob expression... — Charles Duffy
– Charles Duffy, Commented Jan 5, 2021 at 18:47

Barmar · Accepted Answer · 2021-01-05 18:40:35Z

4

The variable is being interpolated properly. The problem is that you're not wrapping it in double quotes, so you're creating invalid JSON.

curl --insecure --header "Content-Type: application/json" \
  --request POST \
  --data '{"email":"'"$EMAIL"'","password":"validPassword"}' \
  http:/ticketing.dev/api/users/signup

When you want to see what the command actually looks like, put echo before curl or run the script with bash -x. You would have seen

--data {"email":[email protected],"password":"validPassword"}

It would be better if you used the jq tool to manipulate JSON in bash scripts.

edited Jan 5, 2021 at 18:40

answered Jan 5, 2021 at 18:38

Barmar

789k57 gold badges555 silver badges669 bronze badges

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

2 Comments

Charles Duffy Over a year ago

Heh, quite right -- I missed the lack of literal double quotes. Still, the email address is there in the body, just not substituted in in a way that makes it valid JSON; so the OP's claim that there's an empty string in its place is confusing to me.

Barmar Over a year ago

This wouldn't be the first time someone didn't debug sufficiently to tell the actual problem.

Collectives™ on Stack Overflow

bash string interpolation returns empty string [duplicate]

1 Answer 1

2 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Linked

Related