Using a variable to execute a curl command

Question

I have a problem when using curl on my linux script:

#!/bin/bash


userName="user";
passWord="password";
tenantName="tenant";

commande="curl -X POST -H \"Content-Type: application/json\" -H 
\"Cache-Control: no-cache\" -H
 \"Postman-Token: 111131da-8254-21b3-1b95-9c12954152c9\" 
-d '{\"auth\":{\"tenantName\":\"$tenantName\",\"passwordCredentials\":
{\"username\":\"$userName\",\"password\":\"$passWord\"}}}'
 \"http://controller:5000/v2.0/tokens\""

When the output of the variable commande is copy pasted into the shell it works, but when i use :

res= $(eval $commande)
#or
res=`$commande`

Neither one of those commands works, and this is the output error i usually get:

line 11: {"access":: command not found

PS: If i do

echo $commande

And then i copy past the result on the shell it works,If anyone can help me that would be great !

Check your spelling first, you have commande in one place, and comande in another. Also {"access": looks like part of a JSON snippet, but your first code snippet doesn't have that anywhere. — ilkkachu
– ilkkachu, Commented Mar 13, 2017 at 12:11
I made a mistake in writing the question but i've fixed it , and my Curl comman is working , the proof is that the output of the $commande variable when copy pasted works perfectly fine on my shell. — Kingofkech
– Kingofkech, Commented Mar 13, 2017 at 12:15
What response do you get from the res=`$commande` instruction? That attempt is less wrong than the other one. — Chris Davies
– Chris Davies, Commented Mar 13, 2017 at 14:25
this is what i get: [ curl: (6) Could not resolve host: no-cache" curl: (6) Could not resolve host: 111131da-8254-21b3-1b95-9c12954152c9" curl: (1) Protocol ""http" not supported or disabled in libcurl] but it works in the console if i try it straight :/ — Kingofkech
– Kingofkech, Commented Mar 13, 2017 at 14:28

chepner · Accepted Answer · 2017-03-13 13:16:41Z

A variable is for data, not code. Define a function. This also simplifies your quoting.

#!/bin/bash

userName="user"
passWord="password"
tenantName="tenant"

commande () {
    curl -X POST \
         -H "Content-Type: application/json" \
         -H "Cache-Control: no-cache" \
         -H "Postman-Token: ..." \
         -d@- \
         http://controller:5000/v2.0/tokens <<EOF
    {
      "auth": {
        "tenantName": "$tenantName",
        "passwordCredentials": {
          "username": "$userName",
          "password": "$password"
        }
      }
    }
EOF
}

The above also reads the JSON from a here-document (@- reads the argument for the -d option from standard input) instead of embedding it in a string to further simplify quoting.

However, it is also a bad idea to hand-code JSON like this if you aren't ensuring that the values of userName, passWord, and tennatnName are properly JSON-encoded. A better solution is to use something like jq to generate proper JSON for you.

commande () {
  json_template='{
    auth: {
      tenantName: $tn,
      passwordCredentials: {
        username: $un,
        password: $pw
      }
    }
  }'
  jq -n --arg un "$userName" \
        --arg pw "$passWord" \
        --arg tn "$tenantName" "$json_template" |
    curl -X POST
         -H "Content-Type: application/json" \
         -H "Cache-Control: no-cache" \
         -H "Postman-Token: ..." \
         -d@- \
         http://controller:5000/v2.0/tokens
}

Does the function commande returns the output of the curl command as i wanted ? — Kingofkech
– Kingofkech, Commented Mar 13, 2017 at 14:11

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