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I am trying to make a script that takes some atom feeds and posts them to slack through the Slack API via curl. What I have now works for simple texts, but some of them have double quotes or & characters in them and that seems to annoy slack API as I get an invalid payload error. Here's my script:

#!/bin/bash
rsstail -i 3 -u "http://MY_FEED_URL" -n 0 | while read line;
do
    # This is just a sample text, it should be ${line}
    data='Something "&" and something do " "';
    payload="payload={\"channel\": \"#my_channel\", \"username\": \"Bot\", \"text\": \"${data}\", \"icon_emoji\": \":ghost:\"}";
    echo ${payload};
    curl \
        -H "Accept: application/json" \
        -X POST \
        -d '${payload}' \
        https://hooks.slack.com/services/xxxx

The output of the "echo" is:

payload={"channel": "#my_channel", "username": "Bot", "text": "Something "&" and something do " "", "icon_emoji": ":ghost:"}

I am not advanced in bash scripting and I need a little bit of help. What am I doing wrong ?

Thanks!

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1 Answer 1

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8

You need to url-encode the data, and the easiest way to do this is to get curl to do it for by replacing the -d option by --data-urlencode. Also, you need to use double quotes or the shell will not expand the variable, so we have

curl \
    -H "Accept: application/json" \
    -X POST \
    --data-urlencode "${payload}" \
    https://hooks.slack.com/services/xxxx

You can also simplify setting payload= by having part of the string inside single quotes, and part within double quotes, provided there is no space between the parts, as in '...'"..."'...'. So, we get

payload='payload={"channel": "#my_channel", "username": "Bot", "text": "'"${data}"'", "icon_emoji": ":ghost:"}'

You probably need to escape the double quotes in data, perhaps with \, as they will be inside "" in a json string.

data='Something \"&\" and something do \" \"'

If you have read your data from the input into variable line, you can do this replacement with bash:

line=${line//\"/\\\"}
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  • I tried your suggestion and still does not work. If I remove the quotes from the string it does. How do I escape the quotes, since they are within the ${line} variable ? Commented Apr 28, 2016 at 17:17
  • In my case I had to remove the shebang. Commented Mar 29, 2020 at 13:57

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